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Acronyms and Abbreviations in Telecommunications and IT Sectors

Find allmost all Acronyms & Abbreviations used in Telecom & IT sectors.

A
A3	GSM Authentication Algorithm
A5	GSM Stream Cipher Algorithm
A8	SM Cipher Key Generating Algorithm (GSM)
AA	Auto Answer
AAA	Authentication, Authorisation, Accounting
AAL	ATM Adaptation Layer
AAR	Automatic Alternate Routing
AARP	AppleTalk Address Resolution Protocol
AARTS	Automatic Audio Remote Test Set
AAV	Alternate Access Vendors
AB	Answer Back
ABC	Advanced Broadband Communications
A-bis	BSC-BTS Interface
ABM	Asynchronous Balanced Mode (HDLC)
ABR	Available Bit Rate (ATM)
ABR	Area Border Router
ABS	Alternate Billing Service
AC	Access Charge
AC	Area Code
AC	Authorisation Code
AC	Access Control (Token Ring FDDI)
AC	Authentication Centre
ACA	Australian Communications Authority
ACA	Automatic Circuit Assurance
ACC	Automatic Callback Calling
ACCH	Associated Control Channel
ACD	Automatic Call Distribution
ACDS	Automatic Call Distribution Systems
ACE	Authentication Encryption
ACE	Advanced Communications Experiments
ACEK	Authentication Encryption Key
ACF	Advanced Communication Function
ACITS	Advisory Committee on Information Technology Standardisation (SOG-IT)
ACK	Acknowledgement
ACNA	Access Carrier Name Abbreviation
ACP	Access Control Point
ACQ	All Call Query (number portability)
ACR	Allowed Cell Rate
ACRE	Authorisation and Call Routing Equipment
ACS	Asynchronous Communications Server
ACSE	Association Control Service Element
ACTE	Approvals Committee for Terminal Equipment
ACTOM	Advisory Committee on Technical and Operational Matters (of Inmarsat)
ACTS	Advanced Communications Technology Satellite
ACTS	Advanced Communications Technologies and Services
ACU	Automatic Calling Unit
AD	Abbreviated Dialling
A-D	Analogue-to-Digital
ADC	Analogue-to-Digital Converter
ADC	Access Deficit Charge or Contribution
ADC	Analogue-to-Digital Conversion
ADCCP	Advanced Data Communications Control Procedures
ADCT	Adaptive Discrete Cosine Transform Coding (video coding)
ADH	Automatic Data Handling
ADIF	Analogue Digital Interface
ADM	Add Drop Multiplexer
ADP	Automatic Data Processing
ADPCM	Adaptive Differential Pulse Code Modulation
ADPE	Automatic Data Processing Equipment
ADPSSO	Automatic Data Processing System Security Officer
ADS	Asynchronous Data Switching
ADSL	Asymmetric Digital Subscriber Line
ADU	Automatic Dialling Unit
ADX	Automatic Data Exchange
AECMA	Association Européenne des Constructeurs de Matériel Aerospatial (European Association for the Construction of Aero-Space Equipment)
AECN	Alternate Exchange Carrier Name (US)
AENOR	Associación Espanola de Normalización (Standards Association Spain)
AEROM	Electrically Alterable Read Only Memory
AF	Audio Frequency
AFC	Area Frequency Coordinator
AFC	Automatic Frequency Control
AFE	Analogue Front End
AFIPS	American Federation of Information Processing Societies
AFMS	Administrative Frequency Management System
AFNOR	Association Française de Normalisation (Standards Association France)
AFUTT	Association Française des Utilisateurs du Téléphone et des Télécommunications (French Telegraphs and Telephone Users’ Association)
AGC	Automatic Gain Control
AGCH	Access Grant Channel
AGCOM	Autorità per le Garanzie nelle Comunicazioni (Italy)
AGE	Aerospace Ground Equipment
AGRAS	Air-Ground Radiotelephone Automated Service
AH	Authentication Header (IPSec security protocol)
AI	Artificial Intelligence
AIM	Amplitude Intensity Modulation
AIM	Ascend Inverse Multiplexing
AIM	Advanced Informatics for Medicine (Application Programme of DG XIII/F)
AIN	Advanced Intelligent Network
AIO	Asynchronous Input/Output
AIOD	Automatic Identification of Outward Dialling
AIP	Application Infrastructure Provider
AIP	Advanced Information Processing
AIP	Advanced Infrastructure Planning
AIS	Automated Information System
AIS	Alarm Indication Signal
AITS	Acknowledged Information Transfer Service (ITU-T)
AJ	Anti-Jamming
AL	Access Line
ALBO	Automatic Line Build Out
ALC	Automatic Level Control
ALC	Automatic Load Control
ALE	Automatic Link Establishment
ALE	Approval Liaison Engineer (UK)
ALEC	Alternative Local Exchange Carrier (US)
ALI	Automatic Location Information
ALI	Analogue Line Interface
ALU	Arithmetic and Logic Unit
AM	Amplitude Modulation
AM/PM/VSB	Amplitude Modulation/Phase Modulation/Vestigial Sideband
AMA	Automatic Messaging Accounting
AMADNS	AMA Data Networking System
AMC	Administrative Management Complex
AME	Amplitude Modulation Equivalent
AME	Automatic Message Exchange
AMI	Alternative Mark Inversion
AMPS	American Mobile Phone System (analogue cellular)
AMPSSO	Automated Message Processing System Security Officer
AMR	Adaptive Multi Rate
AMTS	Automated Maritime Telecommunications System
AN	Annunciator
ANACOM	National Communications Authority (Portugal)
ANATEL	Agência Nacional de Telecomunicações do Brasil (Brazil)
ANC	All Number Calling
ANI	Automatic Number Identification (ISDN)
ANL	Automatic Noise Limiter
ANM	Answer Message
ANR	Automatic Network Routing
ANRC	National Regulatory Authority of Romania
ANRT	Agence Nationale de Réglementation des Telecommunications (Morocco)
ANRTI	National Regulatory Agency in Telecommunications and Informatics (Moldova)
ANS	American National Standard
ANS	Advanced Network Services
ANSI	American National Standards Institute
ANT	ADSL Network Terminator
AOA	Angle of Arrival
AOC	All Ones Code
AOC	Advice of Charge
AOS	Alternative Operator Services
AP	Attendant Position
AP	Anomalous Propagation
AP	Access Point (UPT)
AP	Application Pilot
APA	Access Provider Architecture
APC	Adaptive Predictive Coding
APCM	Adaptive Pulse Code Modulation
APDU	Application Protocol Data Unit
API	Application Programming Interface
APK	Amplitude Phase-Shift Keying
APL	Analogue Private Line
APL	Average Picture Level
APLT	Advanced Private Line Termination
APNSS	Analogue Private Network Signalling System
APON	ATM Passive Optical Network
APP	Applications Portability Profile
APPC	Advanced Program-to-Program Communications
APPN	Advanced Peer-to-Peer Networking
APS	Automatic Protection Switching
APT	Application Pilot Transfer (Group)
APT	Telephony Applications System
AR	Alternative Recall
AR	Access Rate
AR	Alternate Route
ARA	Access Registration Point (UPT)
ARD	Automatic Ring Down
ARDIS	Advanced Radio Data Information Service
ARE	Autorité de Régulation (Mauritania)
ARESEP	Autoridad Reguladora de los Servicios Públicos (Costa Rica)
ARIN	American Registry for Internet Numbers
ARINC	Aeronautical Radio Incorporated (Aviation)
ARM	Asynchronous Response Mode (HDLC)
ARP	Address Resolution Protocol
ARPU	Average Revenue Per User
ARPT	Autorité de Régulation de la Poste et des Telecommunications (Algeria)
ARPTC	Autorité de Régulation de la Poste et des Télécommunications du Congo ( DR Congo)
ARQ	Automatic Repeat Request
ARS	Automatic Route Selection
ARSR	Air Route Surveillance Radar
ART	Audible Ringing Tone
ART	Autorité de Régulation des Telecommunications (France)
ART	Agence de Régulation des Télécommunications (Senegal)
ART&P	Autorité de Réglementation des Secteurs de Postes et Télécommunications (Togo)
ARTEL	Agence de Régulation des Télécommunications (Gabon)
ARTEL	Autorité Nationale de Régulation des Télécommunications (Burkina Faso)
ARU	Audio Response Unit
ARU	Alarm Relay Unit
AS	Analogue Signal
AS	Answer Supervision
AS	Anti Spooling
ASAM	ATM Subscriber Access Multiplexer
ASCI	Advanced Speech Cal Items
ASCII	American Standard Code for Information Interchange
ASCU	Agent-Set Control Unit
ASI	ATM Service Interface
ASIC	Application-Specific Integrated Circuit
ASK	Amplitude Shifting Key
ASN	Auxiliary Signal Network
ASN	ATM Switching Network
ASN.1	Abstract Syntax Notation 1 (ISO)
ASOG	Access Service Ordering Guidelines
ASP	Adjunct Service Point
ASP	Application Service Provider
ASP	Advanced Speech Processor
ASR	Airport Surveillance Radar
ASR	Automatic Send and Receive
ASR	Access Service Request
ASR	Automatic Speech Recognition
ASR	Answer:Seize Ratio
ASTIC	Anti-Sidetone Induction Coil (Circuit)
ASVD	Analogue Simultaneous Voice and Data
AT	Attentuation
AT	Access Tandem
AT	Assistive Technology
AT	Asynchronous Transfer Mode
AT&T	American Telephone and Telegraph Corporation
ATB	All Trunks Busy
ATC	Adaptive Transform Coding
ATCI	Agence des Télécommunications de Côte d’Ivoire
ATD	Asynchronous Time Division Switching
ATDM	Asynchronous Time Division Multiplexing
ATDMA	Advanced Time Division Multiple Access
ATE	Automatic Test Equipment
ATE	Automatic Telephone Exchange
ATH	ATM Transmission Hierarchy
ATIS	Alliance for Telecommunications Industry Solutions
ATIS	Automatic Transmitter Identification System
ATM	Active Traffic Management
ATM	Asynchronous Transfer Mode
ATM	Automated Teller Machine
ATMM	ATM Management Process
ATS	ATM Transmission System
ATSC	Advanced Television Systems Committee
ATU	ADSL Transmission Unit
ATU-C	ADSL Transmission Unit, Central
ATU-R	ADSL Transmission Unit, Remote
ATRP	Telecommunications, Broadcasting and Post Agency (Slovenia)
AU	Alternative Use
AU	Adaptation Unit
AUC	Authentication Centre
AUI	Attachment Unit Interface
AUP	Acceptable Use Policy
AUSM	ATM User Service Module
AUTODIN	Automatic Digital Network
AUTOSEVO- COM	Automatic Secure Voice Communications Network
AUTOVON	Automatic Voice Network
AVD	Alternate Voice Data
AVI	Audio Video Interleave
AVM	ATM Voice Multiplexer
AVM	Audio Visual Management
AW	Administrative Weight
AWG	American Wire Gauge
AWGN	Additive White Gaussian Noise
AXE	Automatic Cross-Connection Equipment (also known as ACE)
B
B2B	Business-to-Business
B2C	Business-to-Consumer
B3ZS	Binary/Bipolar Three Zero Substitution (line-code)
B6ZS	Binary 6-Zero Substitution (line-code)
B8ZS	Binary 8-Zero Substitution (line-code)
BA	Balanced Asynchronous (HDLC)
BA	Basic Access
BABT	British Approvals Board for Telecommunications
BACP	Bandwidth Allocation Control Protocol (PPP ISDN)
BAIC	Barring of All Incoming Calls
BALUN	Balanced, Unbalanced Device
BAOC	Barring of All Outgoing Calls
BAP	Bandwidth Allocation Protocol
BBS	Bulletin Board Service
BBSK	Binary Phase Shift Keying
Bc	Committed Burst
BCA	Bhutan Communications Authority
BCC	Block Check Character
BCCH	Broadcast Control Channel
BCD	Binary-Coded Decimal
B-CDMA	Broadband Code Division Multiple Access
BCF	Budget Cross-Flow Model
BCH	Bose-Chaudhuri-Hocquenghem (forward error correction technique)
BCI	Bit-Count Integrity
BCLB	Broadband Connectionless Bearer Service (ATM)
BCOB	Broadband Connection-Oriented Bearer Service (ATM)
BCPN	Business Customer Premises Network
Bd	Baud
BDCS	Broadband Digital Cross-Connect System
BDF	Building Distribution Frame
BDSL	See VDSL
BDT	Telecommunication Development Bureau of the ITU
BECN	Backward Explicit Congestion Notification
B-ED	Best-Effort Delivery
BEMS	Business Exchange Measured Service
BEP	Back-End Processor
BER	Basic Encoding Rules
BER	Bit Error Rate
BER(T)	Bit Error Rate (Test)
BETRS	Basic Exchange Telecommunications Radio Service
BEX	Broadband Exchange
BFO	Beat Frequency Oscillator
BFWA	Broadband Fixed Wireless Access
BH	Busy Hour
BHCA	Busy Hour Call Attempts
BICC	Bearer Independent Call Control
B-ICI	Broadband Intercarrier Interface (ATM)
BIH	International Time Bureau
BIOS	Basic Input-Output System
BIP	Bit Interleaved Parity
BIPT	Belgian Institute for Posts and Telecommunications
B-ISDN	Broadband Integrated Services Digital Network
BIT	Built-In Test
BITE	Built-In Test Equipment
BIU	Bus Interface Unit
B-LE	Broadband Local Exchange (B-ISDN)
BLEC	Building Local Exchange Carrier (US)
BLER(T)	Block Error Rate (Test)
BLOB	Binary Large Object
BLSR	Bidirectional Line Switch Ring
BNI	Broadband Network Interface
BNM	Broadband Network Module
BNN	Boundary Network Node
BNS	Broadband Network Service
BOC	Bell Operating Company (USA)
BONDING	Bandwidth On Demand Interoperability Group
BOOTP	Bootstrap Protocol
BORSCHT	Battery supply, Overvoltage protection, Ringing current, Supervision, Coding, Hybrid conversion, Testing
BOT	Build-Operate-Transfer Agreement
BP	Band Pass
BP	Bypass
BP	Breakeven Point
BPDU	Bridge Protocol Data Unit
BPI	Baseline Privacy Interface
BPSK	Binary Phase Shifting Key
BPV	Bipolar Violation
BPVR	Bipolar Violation Ratio
BQB	Bluetooth Qualification Body
BQP	Bluetooth Qualification Programme
BR	Radiocommunication Bureau
BRA	Basic Rate Access
BRAS	Broadband Access Server
BRC	Block Redundancy Check
BRF	Bridge Relay Function
BRI	Basic Rate Interface (ISDN)
BRITE	Basic Rate Interface Transmission Equipment
BRLU	Broadband Remote Line Unit
BS	Base Station
BS	Bearer Service
BS	Bellset
BSA	Basic Serving Arrangement
BSA	Business Segmented Accounts
BSC	Base Station Controller
BSC	Binary Synchronous Communication
BSE	Basic Service Element
BSGL	Branch Systems General Licence (UK)
BSI	British Standards Institute
BSIC	Base Transceiver Station Identity Code
BSP	Bell System Practice (US)
BSP	Building Service Provider
BSS	Base Station System / Subsystem
BSS	Basic Synchronised Subset
BSS	Billing Support System
BSS	Broadband Switching System
BSS	Business Support System
BSSMAP	Base Station Systems Management Application Part
BT	Busy Tone
BT	Block Terminal
BT	British Telecommunications PLC
BT	Burst Tolerance (ATM)
B-TA	Broadband Terminal Adapter (B-ISDN)
BTA	Botswana Telecommunications Authority
BTAM	Basic Telecommunications Access Method
B-TE	Broadband Terminal Equipment (B-ISDN)
BTN	Billing Telephone Number
BTNR/BTR	British Telecom Network Requirement
BTO	Build-Transfer-Operate (see also BOT)
BTRC	Bangladesh Telecommunication Regulatory Commission
BTS	Base Transceiver Station Terminal
BUS	Broadcast and Unknown Server
BVI	Bridge Group Virtual Interface
BW	Bandwidth
BXM	Broadband Switch Module
C
C/kT	Carrier-to-Receiver Noise Density
C/O	Cut-Off
C/S	Client/Server
CA	Call Appearance
CA	Certification Authority
CAA	Civil Aviation Authority (UK)
CABS	Carrier Access Billing System
CAC	Carrier Access Code
CAC	Connection Admission Control (ATM)
CACS	Centralised Alarm Control System
CAD	Computer Aided Design
CAE	Computer-Aided Engineering
CAF	Controllable ATM Fabric
CAI	Common Air Interface
CALC	Customer Access Line Charge
CALEA	The Communications Assistance for Law Enforcement Act (US)
CAM	Computer Aided Manufacturing
CAM	Content Addressable Memory
CAMA	Centralised Automatic Message Accounting
CAMEL	Customised Applications for Mobile Network Enhanced Logic
CAN	Campus Area Network
CAN	Competitive Access Network
CAN	Cosmopolitan Area Network
CAP	CAMEL Application Protocol
CAP	Carrierless Amplitude Modulation/Phase Modulation
CAP	Competitive Access Provider
CAP	Customer Administration Panel
CAPEX	Capital Expanditures
CAPI	Common ISDN API
CAPS	Common ISDN API Service
CARS	Cable Antenna Relay Services
CAS	Channel Associated Signalling
CAS	Centralised Attendant Service
CAS	Cordless Access Service
CASE	Computer-Aided Software Engineering
CASE	Computer Aided System Engineering
CASP	Communications Application Service Provider
CAT	Carrier Access Tariff
CATscan	Computed Axial Tomodensitometry Scanner
CATV	Cable Television / Community Antennae Television
CAU	Controlled Access Unit (Token Ring)
CAVE	Cellular Authentication and Voice Encryption
CAZ	Communications Authority of Zambia
CB	Cell Broadcast
CB	Central Battery
CB	Channel Bank
CB	Citizens Band
CBAC	Context-Based Access Control
C-BAT	Cost-Benefit Analysis Toolkit
CBDS	Connectionless Broadband Data Service (ETSI)
CBI	Cross-Border Interconnect
CBR	Constant Bit Rate (ATM)
CBRA	Constant Bit-Rate Adapter
CBS	Central Battery Signalling
CBS	Common Base Station
CBX	Computerised Branch Exchange
CC	Common Carrier (US)
CC	Cost Component
CC	Cross-Connect
CCA	Carrier-Controlled Approach
CCA	Current Cost Accounting
CCB	Call Control Block
CCB	Coin Collecting Box
CCBS	Completion of Calls to Busy Subscribers
CCC	Clear Channel Capability
CCCH	Common Control Channel
CCD	Charge Coupled Device
CCF	Call Control Function
CCH	Connections per Circuit per Hour
CCK	Communications Commission of Kenya
CCIR	Comité Consultatif International de Radiodiffusion (International Radiodiffusion Consultative Committee)
CCIR	Comité Consultatif International des Radiocommunications (Consultative Committee on International Radiocommunications)
CCIS	Common Channel Interoffice Signalling
CITC	Communication and Information Technology Commission (Saudi Arabia)
CCITT	Comité Consultatif International Télégraphique et Téléphonique (Consultative Committee on International Telegraphy and Telephony)
CCL	Continuous Communications Link
CCLC	Carrier Common Line Charge
CCP	Calling Card Platform
CCR	Common Control Redundancy
CCR	Customer Controlled Reconfiguration
CCS	Call Connect System
CCS	Common Channel Signalling
CCS	Hundred Call Seconds per Hour
CCSA	Common Control Switching Arrangement
CCSS6	Common Channel Signalling System No.6
CCSS7	Common Channel Signalling System No.7
CCT	Circuit
CCTV	Closed-Circuit Television
CCU	Common Control Unit
CCW	Cable Cutoff Wavelength
CD	Call Deflection
CD	Carrier Detect
CD ROM	Compact Disc Read Only Memory
CD	Collision Detection (LAN)
CD	Compact Disc
CDAA	Circularly Disposed Antenna Arrays
CDC	Call Directing Code
CDC	Control Data Corporation
CDDI	Copper Distributed Data Interface
CDF	Channel Definition Format
CDF	Combined Distribution Frame
CDF	Cumulative Distribution Function
CDMA	Code Division Multiple Access
CDO	Community Dial Office
CDPD	Cellular Digital Packet Data
CDPSK	Coherent Differential Phase-Shift Keying
CDR	Call Detail Record
CDT	Control Data Terminal
CDU	Central Display Unit
CDV	Cell Delay Variation
CDVT	Cell Delay Variation Tolerance
C-E	Communications-Electronics
CE	Conditioning Equipment
CE	Conformité Européenne (European conformity mark)
CEB	Comité Electrotechnique Belge (Electrotechnical Committee Belgium)
CEC	Commission of the European Communities
CEI	Comitato Electrotecnico Italiano (Electrotechnical Committee Italy)
CEI	Comparably Efficient Interconnection
CEIR	Central Equipment Identity Register
CELEX	European Community Legislation Database
CELP	Code Excited Linear Prediction Compression
CENELEC	Comité Européen de Normalisation Electrotechnique (European Committee for Standardisation and European Committee for Electrotechnical Standardisation)
CENTREX	Central Office Exchange (PBX-like Service)
CEP	Circular Error Probable
CEPT	Conférence Européenne des Postes et Télécommunications (European Conference of Post and Telecommunication Administrations)
CER	Cell Error Ratio
CERN	Centre Européen pour la Recherche Nucléaire (European Centre for Nuclear Research)
CERT	Computer Emergency Response Team
CES	Circuit Emulation Service
CFA	Carrier Facility Assignment
CFB	Call Forward Busy
CFE	Contractor-Furnished Equipment
CFNR	Call Forward No Reply
CFR	Code of Federal Regulations (US)
CFRAD	Cisco Frame Relay Access Device
CFS	Common Functional Specifications
CGI	Common Gateway Interface
CGSA	Cellular Geographical Service Area
CHAP	Challenge Handshake Authentication Protocol
ChR	Channel Reliability
CI	Cell Identity
CI	Computer Interconnect
CIAS	Circuit Inventory and Analysis System
CIC	Carrier Identification Code
CIC	Content Indicator Code
CICS	Customer Information Control System
CID	Caller Identification
CID	Channel ID
CID	Craft Interface Device Terminal
CIDR	Classless Inter-Domain Routing
CIF	Common Intermediate Format
CIFAX	Ciphered Facsimile
CIGREF	Club Informatique des Grandes Entreprises Françaises (IT Society for major French companies)
CILE	Call Information Logging Equipment
CIM	Computer Integrated Manufacturing
CiR	Circuit Reliability
CIR	Channel Impulse Response
CIR	Committed Information Rate
CISPR	International Special Committee on Radio Interference
CIT	Computer Integrated Telephony
CIX	Commercial Internet Exchange
CL	Connectionless
CLASS	Custom Local Area Signalling Service
CLAW	Common Link Access for Workstations
CLE	Customer Local Equipment
CLEC	Competitive Local Exchange Carrier
CLI	Calling Line Identity/Identification
CLI	Command Language Interpreter
CLI	Command Line Interface
CLID	Calling Line Identification (ISDN CLASS)
CLIP	Calling Line Identity Presentation
CLIR	Calling Line Identification Restriction
CLNP	Connectionless Network Protocol (ISO ITU-T)
CLNS	Connectionless Network Service (ISO ITU-T)
CLP	Cell Loss Priority
CLR	Cell Loss Ratio
CLS	Call Logging System
CLTS	Connectionless-Mode Transport Service
CM	Communications Management
CM	Configuration Management
CMA	Communications Management Association
CMA	Construction and Maintenance Agreement
CMC	Coherent Multi Channel (optical transmission)
CMI	Coded Mark Inversion
CMIP	Common Management Information Protocol
CMIS	Common Management Information Service
CMISE	Common Management Information Service Element (ISO)
CMNS	Connection-Mode Network Service
CMOS	Complementary Metal Oxide Semiconductors
CMR	Cellular Mobile Radio
CMRR	Common-Mode Rejection Ratio
CMRS	Commercial Mobile Radio Service
CMT	Comisión del Mercado de las Telecomunicaciones (Spain)
CMT	Connection Management
CMTS	Cable Modem Termination System
CN	Core Network
CNA	Change of Number Announcement
CNAE	Customer Network Access Equipment
CNAM	Caller Name
CNC	Comisión Nacional de Comunicaciones (Argentina)
CNCA	Carrier Non-Compatible Applications
C-Net	Analogue Cellular System Standard
CNI	Calling Number Identification
CNI	Change of Number Interception
CNM	Customer Network Management
CNMS	Customer Network Management System
CNR	Carrier-to-Noise Ratio
CNS	Complementary Network Service
CO	Central Office
CO	Call Office
CO FRAD	Central Office Frame Relay Access Device
COAM	Customer Owned and Maintained Equipment
COAX	Coaxial Cable
COBOL	Common Business-Oriented Language
CoC	Certificate of Conformity
CODEC	Coder/Decoder
CODIT	Code Division Test Bed
COFDM	Coded Orthogonal Frequency Division Multiplex
COFETEL	Comisión Federal de Telecomunicaciones (Mexico)
CTU	Czech Telecommunication Office
COG	Centralised Ordering Group
CO-LAN	Central Office-Based Local Area Network
COLP	Connected Line Identification Presentation
COLR	Connected Line Identification Restriction
COMINT	Communications Intelligence
COMJAM	Communications Jamming
COMPUSEC	Computer Security
ComReg	Commission for Communications Regulation (Ireland)
Comsat	Communications Satellite Corporation
COMSEC	Communications Security
CON	Concentrator
CONATEL	Consejo Nacional de Telecomunicaciones (Ecuador)
CONATEL	Comisión Nacional de Telecomunicaciones (Honduras)
CONATEL	Comisión Nacional de Telecomunicaciones (Paraguay)
CONATEL	Comisión Nacional de Telecomunicaciones (Venezuela)
CONEX	Connectivity Exchange
CONP	Connection-Oriented Network Protocol
CONS	Connection-Oriented Network Service
COO	Cell of Origin
COP	Code of Practice
COPS	Common Open Policy Service
CORBA	Common Object Request Broker Architecture (OMG)
CoS	Class of Service
COSINE	Cooperation for Open Systems Interconnection Networking in Europe (EUREKA-8)
COST	Cooperation for R&D in Science and Technology
COT	Central Office Terminal
COT	Continuity Test (SS7)
COT	Customer Office Terminal
CP	Common Practices
CPAF	Customer Premise Access Facility
CPAS	Cellular Priority Access Services
CPB	Cell Priority Bit
CPC	Calling Party Category
cPCI	Compact Peripheral Component Interconnect
CPCS	Call Processing Control System
CPCS	Common Part Convergence Sublayer
CPE	Customer Premises Equipment
CPI-C	Common Programming Interface for Communications
CPN	Calling Party Number
CPN	Customer Premises Network
CPP	Calling Party Pays
CPS	Carrier Pre-Selection Service
CPS	Cycles per Second (Hertz)
CPSS	Control Packet Switching System
CPT	Compatibility Test
CPU	Central Processing Unit
CPU	Computing and Processing Unit
CQ	Custom Queuing
CQL	Card Query Language
CR	Channel Reliability
CR	Circuit Reliability
CRA	Call Routing Apparatus
CRA	Communications Regulatory Agency (Bosnia and Herzegovina)
CRAFT	Cooperative Research Action For Technology
CRAG	Cellular Radio Advisory Group
CRC	Communications Regulation Commission (Bulgaria)
CRC	Communications Regulatory Commission (Mongolia)
CRC	Cyclic Redundancy Code
CREDFACS	Conduit, Raceway, Equipment Ducts, and FACilitieS. (cabling infrastructure elements)
CRIMP	Cross Impact Model
CRITICOM	Critical Intelligence Communications
CRM	Customer Relationship Management
CROM	Control Read-Only Memory
CRS	Channelised Reserved Services
CRS	Customer Reservation System
CRT	Cathode Ray Tube
CRT	Comisión de Regulación de Telecomunicaciones (Colombia)
CRT	Comité de Régulation des Télécommunications (Mali)
CRT	Connexion au Réseau Terrestre (French switching equipment)
CRTC	Canadian Radio-Television and Telecommunications Commission
CS	Carrier Selection
CS	Carrier System
CS	Circuit Switched
CS1	Capability Set 1
CS2	Capability Set 2
CSA	Called Sub Answered
CSA	Canadian Standards Association
CSA	Carrier Serving Area
CSC	Carrier Selection Code
CSC	Circuit-Switching Centre
CSC	Common Signalling Channel
CSCW	Computer Supported Cooperative Work
CSD	Circuit Switched Data
CSDN	Circuit Switched Data Network
CSDN	Circuit Switched Digital Network
CSE	CAMEL Service Environment
CSF	Customer Service Function
CSI	Called Subscriber Identification
CSI	CAMEL Service Indicator
CSI	Carrier Scale Internetworking
CSI	Customer-Sited Interconnection
CSM	Communications Services Management
CSMA	Carrier Sense Multiple Access
CSMA/CA	Carrier Sense Multiple Access with Collision Avoidance (LAN)
CSMA-CD	Carrier Sense Multiple Access with Collision Detection
CSPDN	Circuit Switched Public Data Network
CSR	Customer Service Representative
CSTA	Computer Supported Telephony Application
CSU	Channel Service Unit
CSU	Circuit Switching Unit
CSU	Customer Service Unit
CSV	Circuit Switched Voice
CT	Call Transfer
CT	Conformance Test
CT	Cordless Telecommunications Mobility
CT	Cordless Telephone
CT	Cross Talk
CT-1	European Analogue Cordless Telephone System
CT-2	Second Generation Digital Cordless Telephone
CTC	Call Termination Charge
CTD	Cell Transfer Delay
CTE	Channel Translation Equipment
CTI	Computer Telephony Integration
CTIA	Cellular Telecommunications Industry Association
CTN	Corporate Telecommunication Network
CTO	Commonwealth Telecommunications Organisation
C-TPS	Cut-Through Packet Switching
CTR	Common Technical Regulations
CTS	Clear to Send / Clear to Transmit
CTS	Conformance Testing Service
CTU	Circuit Terminating Unit
CU	Control Unit
CUG	Closed User Group
CVD	Chemical Vapour Deposition
CVSD	Continuously Variable Slope Delta Modulation
cw	Carrier Wave
cw	Composite Wave
cw	Continuous Wave
CW	Call Waiting
CX	Composite Signalling
cxr	Carrier
D
D/A	Digital-to-Analogue
D/L	Downlink
DA	Demand Analysis
DA	Destination Address (LAN)
DAA	Data Access Arrangement
DAB	Digital Audio Broadcasting
DAC	Dual Attached Concentrator
DACS	Digital Access Cross Connect Service
DAI	Digital Audio Interface (104 kbit/s)
DAL	Direct Access Line
DAM	Dynamic Amplitude Modulation
DAMA	Demand Assigned Multiple Access
D-AMPS	Digital AMPS (also known as IS-136)
DAP	Demand Access Protocol
DARPA	Defense Advanced Research Projects Agency (US)
DAS	Directory Access System
DAS	Dual Attachment Station (FDDI)
DASD	Direct Access Storage Device
DASS	Digital Access Signalling System
DAT	Digital Audio Tape
DATV	Digitally Assisted TV
DAU	Data Adapter Unit
dB	Decibel
dBa	Decibels Adjusted
DBMS	Database Management System
DBS	Direct Broadcasting by Satellite
DBS	Database System
DC	Direct Current
DC	Dry Circuit
DCA	Data Communications Agreement
DCC	Data Communications Channel
DCCH	Dedicated Control Channel
DCD	Data Carrier Detect
DCE	Data Circuit-Terminating Equipment
DCE	Data Communications Equipment
DCE	Distributed Computing Environment
DCF	Data Communications Function Block (TMN)
DCF	Data Count Field
DCL	Direct Communications Link
DCME	Digital Circuit Multiplication Equipment
DCN	Data Communications Network
DCOM	Distributed Component Object Model
DCOSS	Digital Central Office Switch Simulator
DCP	Digital Communications Protocol
DCPN	Domestic Customer Premises Network
DCPSK	Differentially Coherent Phase-Shift Keying
DCS	Digital Cellular System
DCS	Digital Communication Systems
DCS	Digital Crossconnect System
DCS1800	Digital Communications System 1800 MHz
DCT	Discrete Cosine Transform
DCU	Digital Concentrator Unit
DCU	Distribution and Control Unit
DCWV	Direct-Current Working Volts
DDBS	Distributed Data Base System
DDD	Direct Distance Dialling
DDE	Dynamic Data Exchange
DDF	Digital Distribution Frame
DDI	Direct Dialling In
DDM	Digital Data Multiplexer
DDM	Distributed Data Management
DDN	Defense Data Network (US)
DDR	Dial-on-Demand Routing
DDR	Double Data Rate
DDS	Dataphone Digital Service
DDS	Digital Data Service
DDS	Direct Digital Synthesis
DE	Discard Eligible
DECT	Digital Enhanced Cordless Telecommunications
DEK	Data Encryption Key
DEL	Direct Exchange Line
DELTA	Developing European Learning through Technological Advance
DEM	Digital Elevation Model
Demarc	Demarcation Point
demux	Demultiplexer
DEN	Document Enabled Networking
Dequeue	Double-Ended Queue
DES	Data Encryption Standard
DES	Direct Extension Select
DES	Destination End Station
Detem	Detector/Emitter
DF	Directional Finding
DFC	Data Flow Control
DFS	Distributed File System
DFSK	Double-Frequency Shift Keying
DG	Directorate General (European Commission)
DGPS	Differential Global Positioning System
DHCP	Dynamic Host Configuration Protocol
DHTML	Dynamic Hypertext Mark-up Language
DIA	Document Interchange Architecture
DID	Direct Inward Dialling
DIEL	Advisory Committee on Telecommunications for Disabled and Elderly People (UK)
DILIC	Dual Inline Integrated Circuit
DIN	Deutsches Institut für Normung (German Standards Institute)
DIP	Dual In Line Package (integrated circuits)
DIS	Draft International Standard
DISA	Direct Inward System Access
DISN	Defence Information System Network
DISNET	Defence Integrated Secure Network
DJSU	Digital Junction Switching Unit
DKT	Digital Key Telephone
DL	Dial Level
DLC	Digital Loop Carrier
DLCI	Data-Link Connection Identifier
DLCS	Digital Loop Carrier System
DLE	Digital Local Exchange
DLG	Digital Line Graph
DLL	Dynamic Link Library
DLSw	Data Link Switching
DLTE	Digital Local Tandem Exchange
DLU	Digital Line Unit
DM	Delta Modulation
DM	Disconnected Mode (HDLC)
DM	Distributed Management
DMA	Direct Memory Access
DMA	Data Management Amendment
DMB	Dynamic Multipoint Bridging
DMC	Desktop Multimedia Conferencing
DME	Distance Measuring Equipment
DME	Distributed Management Environment
DMI	Distributed Management Interface
DMOQ	Direct Measures of Quality
DMS	Defence Message System
DMS	Digital Multiplex Switch
DMS	Digital Multiplexer System
DMSU	Digital Main Switching Unit
DMT	Discrete Multitone
DMTF	Desktop Management Task Force
DNA	Digital Network Architecture
DNIC	Data Network Identification Code (X121)
DNIS	Dialled Number Identification Service
DNPA	Data Numbering Plan Area
DNS	Domain Name Service
DNSIX	Department of Defense Intelligence Information System
Network Security for Information Exchange (US)
DNU	Digital Networking Unit
DO	Design Objective
DOCSIS	Data Over Cable Services Interface Specifications
DOD	Direct Outward Dialling
DoS	Denial of Service
DOSE	Direction of Arrival by Signal Elimination
DOV	Data Over Voice
DOVE	Data Over Voice Equipment
DP	Dial Pulsing
DP	Dialling Plan
DP	Distribution Point
DPCM	Differential Pulse Code Modulator
DPE	Data Processing Equipment
DPIT	Designated Profile Interoperability Testers
DPNSS	Digital Private Network Signalling System
DPSK	Differential Phase-Shift Keying
DQ	Directory Enquiries Service
DQDB	Distributed Queue Dual Bus
DQPSK	Differential Quadrature Phase Shifting Key
DR	Distortion Ratio
DRAM	Dynamic Random-Access Memory
DRNC	Drift Radio Network Controller
DRSI	Destination Station Routing Indicator
DRX	Discontinuous Reception
DS	Data Set
DS	Digital Signal
DS	Direct Sequence
DS	Direct Support
DS	Dual Signalling (Loop-Disconnect and DTMF)
DS	Duplex Signalling
DSA	Dial Service Assistance
DSA	Data Service Unit
DSA	Directory Service Agent
DSA	Distributed Systems Architecture
DSAP	Destination Service Access Point
DSB	Double-Sideband
DSB-RC	Double-Sideband Reduced Carrier Transmission
DSB-SC	Double-Sideband Suppressed-Carrier Transmission
DSC	Digital Selective Calling
DS-CDMA	Direct-Sequence Code Division Multiple Access
DSCS	Defense Satellite Communications System (US)
DSE	Data Switching Equipment
DSG	Data Systems Group
DSI	Detailed Spectrum Investigation of Radio uUsage (as conducted by CEPT/ERO)
DSI	Digital Speech Interpolation
DSL	Digital Subscriber Line
DSLAM	Digital Subscriber Line Access Multiplexer
DSMA	Digital Sense Multiple Access
DSN	Derived Services Network
DSP	Digital Signal Processor
DSR	Data Signalling Rate
DSRR	Digital Short Range Radio
DSS	Dial Selective Signalling
DSS	Decision Support System
DSS	Digital Subscriber Signalling System (ISDN B-ISDN)
DSS	Digital Switched Services
DSS	Direct Sequence Spread Spectrum
DSS	Direct Station Selection
DSSCS	Defence Special Service Communications System
DSTE	Data Subscriber Terminal Equipment
DSU	Data Service Unit
DSU	Digital Service Units
DSVD	Digital Simultaneous Voice and Data
DT	Data Terminal
DT	Dial Tone
DTAM	Document Transfer and Manipulation (ISO)
DTAP	Direct Transfer Application Part
DTE	Data Terminal Equipment
DTG	Date-Time Group
DTH	Direct-to-Home
DTLU	Digital Terminal Line Unit
DTM	Digital Terrain Model
DTMF	Dual Tone Multi Frequency
DTN	Data Transmission Network
DTP	Detail Test Plan
DTS	Digital Transmission System
DTU	Data Transfer Unit
DTU	Data Tape Unit
DTU	Direct to User
DTV	Digital Television
DTX	Discontinuous Transmission
DUA	Directory User Agent
DVB	Digital Video Broadcasting
DVL	Direct Voice Link
DVM	Data over Voice Multiplexer
DVMRP	Distance Vector Multicast Routing Protocol
DVRA	Distance Vector Routing Algorithm
DVT	Digital Video Terminal
DWDM	Dense Wavelength Division Multiplexing
DWMT	Discreet Wavelet Multi-Tone
DXC	Digital Cross Contact
DXI	Data Exchange Interface (ATM SMDS)
E
E&M	Ear and Mouth (handset)
E&M	Earth and Magnet
E&M	Receive and Transmit (signalling)
E/O	Electro-Optical Conversion
E2E	End-to-End
EA	Evaluation Authority
EACEM	European Association of Consumer Electronics Manufacturers
EAI	Emergency Access Interface
EAI	Enterprise Application Integration
EAS	Extended Area Service
EBC	Element-Based Charging
EBIT	European Broadband Interconnection Trial
EBITDA	Earnings before Income Tax, Depreciation and Amortisation
EBO	Embedded Base Organisation
E-Bone	European Backbone (Pan-European Network Backbone Service)
EBS	Emergency Broadcast System
EBU	European Broadcasting Union
EBX	Electronic Branch Exchange
EC	Earth Coverage
EC	Earth Curvature
ECBF	European Citizen’s Band Federation
ECC	Electronically Controlled Coupling
ECC	Enhanced Call Completion
ECCA	European Cable Communication Association
ECCM	Electronic Counter-Countermeasures
ECET	European Country in Economic Transition
ECFRN	European Consultative Forum for Research Networking
ECHO	European Commission Host Organisation
ECI	European Cooperation in Informatics
ECIP	European Cooperation in Information Processing
ECITC	European Committee for IT Testing and Certification
ECM	Electronic Countermeasures
ECMA	European Computer Manufacturers’ Association
ECP	European Common Proposal
ECS	European Communications Satellite
ECSA	European Computing Software Association
ECSA	Exchange Carriers’ Standards Association (now ATIS)
ECTA	European Competitive Telecommunications Association
ECTEL	European Conference of Telecommunications and Electronics Industries
ECTEL	National Telecommunications Regulatory Commission (Grenada)
ECTF	Enterprise Computer Telephony Forum
ECTRA	European Committee for Telecommunications Regulatory Affairs
ECTS	Electronic Custom Telephone System
ECTUA	European Council of Telecommunications Users’ Association
EDC	Error Detection and Correction
EDGE	Enhanced Data-Rates for GSM Evolution
EDH	Electronic Document Handling
EDI	Electronic Data Interchange
EDIFACT	Electronic Data Interchange for Administration Commerce and Trade (ANSI)
EDM	Electronic Distance Measurement
EDNS	Enterprise Defined Network Services
EDP	Electronic Data Processing
EDTV	Extended-Definition Television
EECM	End-to-End Call Manager
EEHO	Either End Hop Off
EEMA	European Electronic Mail Association
EEPROM	Electrically Erasable Programmable Read-Only Memory
EEROM	Electronically Erasable Read-Only Memory
EESS	Earth Exploration-Satellite Service
EETT	National Committee of Communications & Posts (Greece)
EF&I	Engineering, Furnishing and Installation
EFCI	Explicit Forward Congestion Indication
EFF	Electronic Frontier Foundation
EFR	Enhanced Full Rate
EFS	End of Frame Sequence (LAN)
EFT	Electronic Funds Transfer
EFTA	European Free Trade Association
EFTPOS	Electronic Funds Transfer at Point of Sale
EGP	Exterior Gateway Protocol
EGSM	Extended Global System for Mobile Communications
EH	Electronic Highways
EHF	Extremely High Frequency
EI	Engineering Instruction
EI	Expansion Interface
EIA	Electronics Industry Association
EIB	European Investment Bank
EICTA	European Information Communications Technology Industry Association
EIR	Equipment Identity Register
EIRP	Effective or Equivalent Isotropically Radiated Power
EIS	Emergency Information System
EISA	Extended Industry Standard Architecture
EIUF	European ISDN User Forum
EKTS	Electronic Key Telephone Sets
EL	Elevation
ELAN	Emulated LAN
ELB	Emergency Location Beacon
EL-display	Electro-Luminescent Display
ELECTRO- OPTINT	Electro-Optical Intelligence
ELF	Extremely Low Frequency
ELINT	Electronics/Electromagnetic Intelligence
ELMI	Enhanced Local Management Interface
ELR	Earth Leg Recall
ELSEC	Electronics Security
ELT	Emergency Locator Transmitter
EMA	Electronic Messaging Association
EMA	Enterprise Management Architecture
EMAG	ETSI MIS Advisory Group
EMC	Electromagnetic Compatibility
EMCON	Emission Control
EMD	Equilibrium Mode Distribution
EME	Electromagnetic Environment
EMI	Electromagnetic Interference
EML/EMS	Element Management Layer/ Element Management Service
EMP	Electromagnetic Pulse
EMR	Electromagnetic Radiation
EMRP	Equivalent Monopole Radiated Power
EMS	Electronic Message System
EMS	Enhanced Messaging Services
EMS	Expanded Memory Specification
EMSEC	Emanations Security
EMU	Electromagnetic Unit
EMV	Electromagnetic Vulnerability
EMW	Electromagnetic Warfare
EMW	Electromagnetic Wave
EN	Norme Européenne (European Standard)
ENF	European Numbering Forum
ENFIA	Exchange Network Facilities For Interstate Access (US)
ENG/OB	Electronic News Gathering/Outside Broadcast
ENO	European Numbering Office
ENS	Enhanced Network Services
ENS	Enterprise Network Services
ENSO	ETSI National Standardisation Organisations (ETSI)
ENV	European Pre-standard
EO	End Office
EO	Executive Order
EOC	Embedded Operation Channel
EOD	End of Data
EOF	End of File
EOL	End of Line
EOM	End of Message
EOP	End of Program
EOP	End Output
EOS	End of Selection
EOT	End of Tape
EOT	End of Transmission
EOTC	European Organisation for Testing and Certification
EOW	Engineering Orderwire
EPD	Early Packet Discard
EPI	External Provisioning Interface
EPIRB	Emergency Position Indicating Radio Beacons
EPMU	Equal Proportionate Mark-Up
EPOST	Electronic Point of Sale Terminal
EPROM	Erasable Programmable Read-Only Memory
EPS	End of Frame Sequence (LAN)
EPSCS	Enhanced Private Switched Communications System
ER	Earth Recall
ER	Explicit Rate
ER	Essential Requirement
ERC	European Radiocommunications Committee
ERDF	European Regional Development Fund
ERG	European Regulators’ Group
ERL	Echo Return Loss
ERLINK	Emergency Response Link
ERMES	European Radio Message System (standard for pagers)
ERO	European Radiocommunications Office
ERP	Effective Radiated Power
ERP	Enterprise Resource Planning
ES	End System
ES	Expert System
ESA	European Space Agency
ESAC	Emergency Switch Assistance Centre
ESB	European Standardisation Board
ESC	Enhanced Satellite Capability
ESC	European Standardisation Council
ESCON	Enterprise System Connection (IBM)
ESD	Electrostatic Discharge
ESD	European Standards Database
ESDI	Enhanced Small Device Interface
ESF	European Science Foundation
ESF	Extended SuperFrame
ESI	End System Identifier (ATM ISO)
ESIG	European SMDS Interest Group
ESM	Electronic Warfare Support Measures
ESMR	Enhanced Specialised Mobile Radio
ESMTP	Extended Simple Mail Transfer Protocol
ESN	Equipment Serial Number
ESO	European Standardisation Organisation
ESP	EBIT Service Project
ESP	Encapsulating Security Payload (IPSec security protocol)
ESP	Enhanced Service Provider
ESP	Extended Services Processor
ESPRIT	European Strategic Programme for Research and Development
ESRP	Ente Regulador de los Servicios Públicos (Panama)
ESS	Electronic Switching System
ESS	European Standardisation System
ETACS	Extended Total Access System
ETCI	Electro-Technical Council of Ireland
ETD	Extension Trunk Dialling
E-TDMA	Enhanced TDMA
ETN	Electronic Tandem Network
ETNO	Association of European Public Telecommunications Network Operators
ETO	European Telecommunications Office
ETP	European Telecommunications Platform
ETR	ETSI Technical Report
ETS	Emergency Telecommunications Services
ETS	European Telecommunications Standard
ETSA	European Telecommunication Services Association
ETSI	European Telecommunications Standard Institute
EUMETSAT	European Meteorological Satellite Organisation
EUREKA	European Research Co-operation Agency
EUREKA-95	European Research Project on HDTV
EURESCOM	European Institute for Research and Strategic Studies in Telecommunications
EUROBIT	European Association of Manufacturers of Business Machines and Data Processing Equipment
EurOSINET	European OSI Network
EUSIDIC	European Association of Information Services
EUTELSAT	European Telecommunications Satellite Organisation
EV	European Videocommunications
EW	Electronic Warfare
EWOS	European Workshop for Open Systems
EWP	ETSI Work Programme
EXCSA	Exchange Carriers Standards Association
EXZ	Excessive Zeros
F
F	Frequency
FAA	Federal Aviation Administration (US)
FAC	Fully Allocated Costs
FACCH	Fast Association Control Channel
FAN	Flexible Access Network
FAQ	Frequently Asked Questions
FAS	Frame Alignment Sequence (T-1 and E1)
FB	Framing Bit
FC	Fibre Channel
FC	Frame Control
FC	Functional Component
FCAPS	Fault, Configuration, Accounts, Performance, Security (ISO)
FCC	Federal Communications Commission (USA)
FCCH	Forward Control Channel
FCS	Federation of Communications Services (UK)
FCS	Frame Check Sequence
FD	Full Duplex
FDC	Fully-Distributed Costs
FDD	Frequency Division Duplex
FDDI	Fibre Distributed Data Interface
FDHM	Full Duration at Half Maximum
FDM	Frequency Division Multiplexing
FDMA	Frequency Division Multiple Access
FDMMA	Frequency Division Multiplexing Multiple Access
FDP	Floor Distribution Point
FDX	Full Duplex
FEC	Forward Error Correction
FECN	Forward Explicit Congestion Notification
FED-STD	Federal Standard (US)
FEI	Federation of the Electronics Industry (UK)
FEMA	Federal Emergency Management Agency (US)
FEP	Front-End Processor
FET	Field Effect Transistor
FEXT	Far End Cross Talk
FFSK	Fast FSK
FFT	Fast Fourier Transform
FG	Feature Group
FH	Frequency-Hopping
FH/DS	Frequency-Hopping Direct Sequence
FHSS	Frequency-Hopping Spread Sequence
FIAG	Framework Interconnection Agreement Guidelines
FIB	Focused Ion Beam
FICORA	Finnish Communications Regulatory Authority
FIFO	First In/First Out
FIPS	Federal Information Processing Standards
FIR	Finite Impulse Response
FIRMR	Federal Information Resources Management Regulations
FITL	Fibre In The Loop
FLOPS	Floating-Point Operations Per Second
FLS	Fallback/Fall-Forward Line Sensing
FLT	Full Line Terminal Multiplexer
FM	Frequency Modulation
FM	Function Management
FMC	Fixed Mobile Convergence
FMH	Function Management Header (SNA)
FMS	Fraud Management System
FNC	Federal Networking Council (US)
FO	Fibre Optic
FOC	Final Operational Capability
FOC	Full Operational Capability
FOD	Fax on Demand
FoIP	Fax over Internet Protocol
FOIRL	Fibre Optic Interrepeater Link
FOT	Frequency of Optimum Transmission
FOTP	Fibre Optic Transmittance Procedure
FOTS	Fibre Optics Transmission Systems
FPD	Flat Panel Display
FPIS	Forward Propagation Ionospheric Scatter
FPLMTS	Future Public Land Mobile Telecommunication System
FR	Frame Relay
FR	Frequency Response
FRAD	Frame Relay Assembler/ Disassembler
FRAD	Frame Relay Access Device
FRASM	Frame Relay Access Service Module
FRBS	Frame Relay Bearer Service
FRF	Frame Relay Forum
FRIACO	Flat Rate Internet Access Call Origination
FRM	Functional Reference Model
FRS	Frame Relay Service
FRS	Frame Relay Switch
FSAN	Full Service Access Network
FSDPSK	Filtered Symmetric Differential Phase-Shift Keying
FSK	Frequency Shifting Sequence
FSL	Flexible Service Logic
FSS	Fixed-Satellite Service
FT	Fibre Optic T-Carrier
FT1	Fractional T1
FTAM	File Transfer Access & Management
FTF	Federal Telecommunications Fund (US)
FTP	File Transfer Protocol
FTPF	File Transfer Protocol Filter
FTS	Federal Telecommunications System (US)
FTSC	Federal Telecommunications Standards Committee (US)
FTTB	Fibre to the Building
FTTC	Fibre to the Curb (North America)
FTTCab	Fibre to the Cabinet
FTTEx	Fibre to the Exchange
FTTH	Fibre to the Home
FTTK	Fibre to the Kerb (UK)
FTTN	Fibre to the Neighbourhood
FUNI	Frame User-to-Network Interface (ATM)
FVC	Forward Voice Channel
FWA	Fixed Wireless Access
FWHM	Full Width At Half Maximum
FWM	Four Wave Mixing
FX	Fixed Service
FX	Foreign Exchange Service
FXO	Foreign Exchange Office
FXS	Foreign Exchange Station
G
G.lite	G.992.2 Standard for Asymmetric DSL Technology
G/T	Antenna Gain-to-Noise-Temperature
GA	General Assembly (ETSI)
GAC	Governmental Advisory Committee (ICANN)
GAN	Global Area Network
GAP	Generic Access Profiles
GASP	Gatekeeper Synchronisation Protocol
GATT	Global Agreement on Tariffs and Trade
GBH	Group Busy Hour
GCAC	Generic Connection Admission Control
GCC	Generic Conference Control
GCCC	Global Customer Care Center
GCRA	Generic Call Rate Algorithm
GDF	Group Distribution Frame
GDS	Generic Digital Services
GEA	Gigabit Ethernet Alliance
GEN	Global European Network
GEO	Geostationary Earth Orbit
GETS	Government Emergency Telecommunications Service
GFC	Generic Flow Control (ATM)
GFI	Genera Format Identifier (X25)
GGCL	Government-to-Government Communications Link
GGP	Gateway-to-Gateway Protocol
GGSN	Gateway GPRS Support Node
GIBN	Global Interoperability of Broadband Networks
GII	Global Information Infrastructure
GIO	General Interest Obligations
GIO	Generic Interface for Operations (SMDS)
GIS	Geographical Information System
GIX	Global Internet eXchange
GLONASS	Global Navigation Satellite System
GMDSS	Global Maritime Distress and Safety System
GMPCS	Global Mobile Personal Communication by Satellite
GMRS	General Mobile Radio Service
GMSC	Gateway Mobile Services Switching Centre
GMSK	Gaussian Minimum Shifting Keying
GNCC	Georgian National Communications Commission
GNOC	Global Network Operation Centre
GNS	Get Nearest Server
GOF	Glass Optical Fibre
GoS	Grade of Service
GOSIP	Government Open Systems Interconnection Profile
GPIB	General Purpose Interface Bus
GPRS	General Packet Radio Service
GPS	Global Positioning System
GR	GPRS Register
GRE	Generic Routing Encapsulation
GRX	GPRS Roaming Exchange
GS	Ground-Start Signalling
GSA	General Services Administration (US)
GSA	Global Mobile Suppliers Association
GSA	GSM System Area
GSLB	Groupe Spécial Large Bande (CEPT group on broadband telecommunications)
GSM	Global System for Mobile (second-geration mobile telephony standard)
GSM MS	GSM Mobile Station
GSM PLMN	GSM Public Land Mobile Network
GSM900	Global System for Mobile 900 MHz
GSMP	Global Service Management Platform
GSM-R	GSM for Railways
GSN	GPRS Support Node
GSO	Geostationary Orbit
GSS	Generic Service State
GSS	Group Switching Subsystem
GSTN	General Switched Telephone Network
GTD	Geometric Theory of Diffraction
GTP	Government Telecommunications Programme
GTP	GPRS Tunnelling Protocol
GTR	General Technical Requirements (Russia)
GTS	Government Telecommunications System
GVPN	Global Virtual Private Network
H
H Channel	High-Speed Channel (ISDN)
HACMP	High-Availability Cluster Multiprocessing
HARCENELEC	Agreement for Electrical Cords and Cables
HBN	High Bandwidth Networking
HBS	Home Base Station
HCA	Historic Cost Accounting
HCDS	High-Capacity Digital Services
HCM	High Capacity Multiplexing
HCS	Hard Clad Silica [fibre]
HCSPR	Hundred Call Seconds Per Hour
HCV	High Capacity Voice
HD	Half Duplex
HD	Harmonic Distortion
HDDV	High Definition Digital Video
HDF	Hand-Over Distribution Facility
HDLC	High-Level Data Link Control
HDML	Handheld Device Markup Language
HDSL	High-Data-Rate Digital Subscriber Line
HDT	Host Digital Terminal
HDTM	Half-Duplex Transmission Module (X25)
HDTV	High Definition Television
HDWDM	High Density Wavelength Division Multiplex
HDX	Half-Duplex
HEC	Header Error Control
HEHO	Head End Hop Off
HEMP	High-Altitude Electromagnetic Pulse
HEPnet	High-Energy Physics Network
HERF	Hazards of Electromagnetic Radiation to Fuel
HERO	Hazards of Electromagnetic Radiation to Ordnance
HERP	Hazards of Electromagnetic Radiation to Personnel
HES	Home Electronic System(s)
HF	High Frequency
HFC	Hybrid Fibre/Coax
HFDF	High-Frequency Distribution Frame
HIC	Head-End Interface Converter
HiCap	High-Capacity Digital Services
HIPERLAN	High Performance Local Area Network
HIPPI	High Performance Parallel Interface
HIS	Hospital Information System
HLC	High Layer Compatibility (ISDN)
HLC	High Level Committee (ITU)
HLL	High Level Language
HLR	Home Location Register
HNPA	Home Numbering Plan Area
HOSTID	Host Identifier
HP/PN	Hybrid Private/Public Networking
HPC	High Probability of Completion
HPLMN	Home Public Land Mobile Network
HPPI	High-Performance Parallel Interface
HPR	High Performance Routing
HS	High Speed
HSC	Hierarchical Cell Structure
HSCSD	High Speed Circuit Switched Data
HSCSD	High Speed Circuit Switched Data
HSLAN	High Speed LAN
HSPSD	High-Speed Packet Switched Data
HSSI	High-Speed Serial Interface (ANSI)
HTML	Hypertext Markup Language
HTTP	Hypertext Transfer Protocol (IETF)
HV	High Voltage
HW	Hardware
I
I&A	Identification and Authentication
I&C	Installation and Checkout
I&M	Installation and Maintenance
I/F	Interface
I/O	Input/Output
IA	International Alphabet [CCITT]
IAB	Internet Architecture Board
IAC	Install and Commission
IACS	Integrated Access and Crossconnect System
IAFIS	Integrated Automated Fingerprint Identification System
IAHC	Internet International Ad Hoc Committee
IAM	Initial Address Message (SS7)
IANA	Internet Address Naming Authority
IARU	International Amateur Radio Union
IBC	Integrated Broadband Communication
IBCN	Integrated Broadband Communications Network
IBN	Integrated Broadband Network
IBS	International Business Service (INTELSAT)
IC	Incoming
IC	Integrated Circuit
IC	Interconnect
ICANN	Internet Corporation for Assigned Names and Numbers
ICASA	Independent Communications Authority of South Africa
ICCB	Internet Control and Configuration Board
ICD	Internal Cable Distribution
ICD	International Code Designator (ISO)
ICGB	Institut des Communications de la Guinée-Bissau
ICI	Incoming Call Identification
ICI	Intercarrier Interface (SMDS)
ICI	Interexchange Carrier Interface (US)
ICMP	Internet Control Message Protocol
ICNI	Integrated Communications, Navigation, and Identification
ICP	Internet Control Protocol
ICR	Initial Cell Rate
ICR	Intelligent Call Routing
ICS	Implementation Conformance Statement
ICS	Intelligent Calling System
ID	Identification
ICSA	International Computer Security Association
ICT	Information and Communication Technologies
ICTA	Information and Communication Technologies Authority (Mauritius)
ICW	Interrupted Continuous Wave
ID	Identification
IDA	Infocomm Development Authority of Singapore
IDA	Integrated Data Access
IDC	Insulation Displacement Connection
IDD	International Direct Dialling
IDDD	International Direct Distance Dialling
IDDD	International Direct Dialling Designator
IDEN	Integrated Dispatch Enhanced Network
IDF	Intermediate Distribution Frame
IDI	Initial Domain Identifier (ISO)
IDLC	Integrated Digital Loop Carrier (Telephony)
IDN	Integrated Digital Network
IDNX	Integrated Digital Network Exchange
IDP	Initial Domain Part
IDP	Internet Datagram Protocol
IDPR	Inter-Domain Policy Routing
IDR	Intermediate Data Rate/Intelsat Digital Route
IDS	Intrusion Detection System
IDTV	Improved-Definition Television
IE	Information Element
IEC	Interconnection Extension Circuit
IEC	Interexchange Carrier
IEC	International Electrotechnical Commission
IEE	Institution of Electrical Engineers (UK)
IEEE	Institute of Electrical and Electronic Engineers (UK)
IEPG	Internet Engineering Planning Group
IES	Industry Executive Subcommittee
IES	Information Exchange Services
IESG	Internet Engineering Steering Group
IETF	Internet Engineering Task Force
IETF	Internet Engineering Task Force
I-ETS	Interim European Telecommunications Standard
IF	Intermediate Frequency
IFFT	Inverse FFT
IFIP	International Federation for Information Processing
IFL	International Frequency List
IFRB	International Frequency Registration Board (now Radio Regulations Board )
IFS	Ionospheric Forward Scatter
IGMP	Internet Group Management Protocol
IGP	Internet Gateway Protocol
IGRP	Interior Gateway Routing Protocol
IHL	Internet Header Length (IP)
IHS	In-House System
IIR	Infinite Impulse Response
IIT	Integrated Information Transport
IITF	Information Infrastructure Task Force
IKE	Internet Key Exchange
ILD	International Long Distance
ILEC	Incumbent Local Exchange Carrier (US)
ILR	Institut Luxembourgeois de Régulation
IM	Instant Messaging
IM	Intensity Modulation
IM	Intermodulation
IMA	Invere Multiplexing over ATM
IMAP	Internet Message Access Protocol
IMCC	ISDN Management and Co-ordinating Committee
IMD	Intermodulation Distortion
IME	International Mobile Station Equipment Identity
IMEI	International Mobile Equipment Identity
IMN	Intelligent Mobile Network
IMO	International Maritime Organisation
IMP	Interface Message Processor
IMP	Intermodulation Products
IMS	Internet Management System
IMSI	International Mobile Station Identity
IMSI	International Mobile Subscriber Identity
IMT	International Mobile Telecommunications
IMTC	International Multimedia Conferencing Consortium
IMTS	Improved Mobile Telephone Service
IMUX	Intelligent Multiplexer
IMUX	Inverse Multiplexer
IN	Intelligent Network (AIN)
INA	Information Networking Architecture
INACOM	Institut Angolais des Communications (Angola)
INAP	Intelligent Network Application Part
INCA	Inter Network Call Accounting system
INCM	Instituto Nacional das Comunicações de Moçambique (Mozambique)
INE	Intelligent Network Element
INFOSEC	Information Systems Security
INLSP	Integrated Net Layer Security Protocol
INMARSAT	International Marine Satellite Organisation
INMS	Integrated Network Management System
INS	Inertial Navigation System
INTAP	Interoperability Technology Association for Information Processing
INTELSAT	International Satellite Organisation
INTT	Instance Nationale des Télécommunications (Tunisia)
INTUG	International Telecommunications User Group
INWATS	Inward Wide-Area Telephone Service
IO	Input/Output
IOC	Integrated Optical Circuit
IOC	Independent Operating Company (US)
IOC	Initial Operational Capability
IOC	Input-Output Controller
IOC	Inter Office Channel
IOCC	I/O Channel Controller
ION	Integrated Optical Network
IONL	Internal Organisation of the Network Layer
IOPS	Internet Operators’ Providers Services
IOT	Inter-Office Trunk
IP	Intellectual Property
IP	Intelligent Peripheral
IP	Interexchange Plant
IP	Internet Protocol
IPA	Intermediate Power Amplifier
IPC	Information Processing Center
IPC	Interprocess Communication
IPCP	Internet Protocol Control Protocol
IPM	Impulses Per Minute
IPM	Interference Prediction Model
IPM	Internal Polarisation Modulation
IPM	Interruptions Per Minute
IPN	Intelligent Peripheral Node
IPNS	ISDN PBX Networking Specification
IPoATM	Internet Protocol over ATM
IPR	Intellectual Property Rights
IPS	Instructions Per Second
ips	Interruptions Per Second
IPSec	Internet Protocol Security
IPSO	IP Security Option
IPT	Internet Protocol Telephony
IPv6	Internet Protocol Version 6
IPX	Internetwork Packet Exchange (NetWare)
IQF	Intrinsic Quality Factor
IR	Infrared
IR	Internet Registry
IRAC	Interdepartment Radio Advisory Committee
IRAS	Internet Routing and Access Service
IRB	Integrated Routing and Bridging
IRC	International Record Carrier
IRC	Internet Relay Chat
IrDA	Infrared Data Association
IRG	Independent Regulators’ Group (Europe)
IrLAN	Infrared LAN
IrLAP	Infrared Link Access Protocol
IRN	Intermediate Routing Node
IRP	Independent Routing Processor
IRPA	International Radiation Protection Association
IRQ	Interrupt Request
IRR	Internal Rate of Return (Financial Modelling)
IRSG	Internet Research Steering Group
IRT	Integrated Rural Telematics
IRTA	Integrated Regional Telematics Architecture
IRTF	Internet Research Task Force
IS	In-Service
IS	Information Systems
IS	Interim Standard (ISO)
IS	Intermediate System (ISO)
ISA	Industry Standard Architecture
ISAC	Information Society Activity Centre (European Commission)
ISB	Independent Side Band
ISC	International Switching Centre
ISD	International Subscriber Dialling (now IDD)
ISDN	Integrated Services Digital Network
ISE	Integrated Service Engineering
ISI	In Span Interconnection
IS-IS	Intermediate System-to-Intermediate System
ISL	Inter-Switch Link
ISM	Industrial, Scientific, and Medical (applications and frequency bands)
ISM	Internetwork Status Monitor
ISM	ISDN Standards Management
ISN	Information Systems Network
ISO	International Organisation for Standardisation
ISOC	Internet Society
ISP	Internet Service Provider
IS-PBX	Integrated Services Private Branch Exchange
ISPO	Information Society Promotion Office (European Commission)
ISR	International Simple Resale
ISSI	Inter-Switching System Interface
ISUP	ISDN User Part
ISV	Independent Software Vendor
ISVR	International Simple Voice Resale
IT	Information Technology
IT	Information Type
IT&T	Information Technologies & Telecommunications
ITA	International Telegraph Alphabet
ITC	International Teletraffic Congress
ITM	Isochronous Transmission
ITN	Independent Telecommunication Network
ITR	Intelligent Text Retrieval
ITS	Insertion Test Signal
ITS	Institute for Telecommunication Sciences
ITSC	Interregional Telecommunications Standards Conference
ITSO	International Telecommunications Satellite Organisation
ITSP	Internet Service Telephony Provider
ITST	National IT and Telecom Agency (Denmark)
ITSTC	Information Technology Steering Committee
ITT&B	Information Technologies Telecommunications & Broadcasting
ITU	International Telecommunications Union
ITU-R	International Telecommunication Union- Radiocommunications
ITU-T	International Telecommunication Union- Telecommunications
ITUSA	Information Technology Users Standards Association
IUC	Interconnection Usage Charge
IVDM	Integrated Voice Data Multiplexer
IVDS	Interactive Video Data Services
IVDT	Integrated Voice and Data Terminal
IVN	Intervening Network (ETSI)
IVPN	International Virtual Private Networks
IVR	Interactive Voice Response
IVS	Interactive Video Service
IWF	Inter-Working Function
IWU	Inter-Working Unit (ETSI TC BT)
IXC	Inter-Exchange Mileage
IXC	Inter-Exchange Carrier (US)
IXIT	Implementation Extra Information for Testing
J
JADSL	ADSL for ISDN
JANET	Joint Academic Network (UK)
JCCR	Joint Committee on Cellular Roaming
JCG	Joint Co-ordination Group (CEN/CENELEC/ETSI)
JDBC	Java Database Connectivity
JDC	Japan’s Digital Cellular
JEEC	Joint ECMA ETSI Programme Committee
JIT	Just In Time
JPEG	Joint Photographic Experts Group (ISO)
JRTIC	Joint Radiophone Technical Interfaces Group
JSC	Joint Spectrum Centre (US)
JTACS	Japanese TACS System
JTC	Joint Technical Committee (EBU/ETSI and ISO/IEC)
JTCG	Joint Technical Co-ordination Group
JTM	Job Transfer and Management
JUNET	Japan UNIX Network Nationwide
K
K/D	Keyboard/Display
KA	Keep Alive Signal
Kbps	Kilo bits per second
KBS	Knowledge-Based System
KCC	Korea Communications Commission
KDC	Key Distribution Centre
KDR	Keyboard Data Recorder
KDS	Key Distribution Service
kHz	Kilohertz
KMC	Key Management Centre
KS	Kearny Specification (US)
KSR	Keyboard Send/Receive Device
KSU	Key Service Unit
kT	Noise Power Density
KTS	Key Telephone System
KTU	Key Telephone Unit
L
l/m	Lines per Minute
L1	Layer 1 (physical layer)
L2	Layer 2 (data link layer)
L3	Layer 3 (network layer)
LADS	Local Area Data Service
LAI	Location Area Identification or Identity
LAMs	Line Adaptor Modules
LAN	Local Area Network
LANE	LAN emulation
LANS	Local Area Network Services
LAP	Link Access Procedure (X25)
LAP-B	Link Access Protocol-Balanced
LAPD	Link Access Procedure for the D-channel (ISDN)
LAPF	Link Access Procedure to Frame mode bearer services (FR ISDN)
LAPM	Link Access Procedure for Modems (V42)
LAPX	Link Access Procedure Half-Duplex (X32)
LASS	Local Area Signalling Services
LATA	Local Access and Transport Area (US)
LATS	Loop Access Test System
LB	Local Battery
LBA	Location Based Advertising
LBO	Line Buildout
LBS	Location-Based Services
LC	Limited Capability
LCD	Liquid Crystal Display
LCI	Logical Channel Identifier
LCM	Line Concentrator Module
LCN	Local Communication Network
LCN	Logical Channel Number (X25)
LCP	Link Control Protocol
LCR	Least Cost Routing
LCV	Line Code Violation
LD	Long Distance
LD	Loop Dial
LD	Loop Disconnect
LDC	Long Distance Carrier
LDCELP	Low-Delay Code Excited Linear Prediction Compression
LDDI	Local Distributed Data Interface (ANSI)
LDM	Limited Distance Modem
LDN	Listed Directory Number
LE	Local Exchange (ISDN)
LE_ARP	LAN Emulation Address Resolution Protocol Protocol
LEC	LAN Emulation Client.
LEC	Local Exchange Carrier
LECS	LAN Emulation Configuration Server
LEO	Low Earth Orbit
LEOS	Low Earth Orbit Satellites
LES	LAN Emulation Server
LF	Low Frequency
LFB	Look-Ahead-For-Busy
LFR	Less Favoured Region
LI	Length Indicator
LIDB	Line Information Database (ISDN)
LIFO	Last In First Out
LIMO	Limited Mobility
LIS	Logical IP Subnet
LJU	Line Jack Unit
LL	Leased Lines
LLB	Line LoopBack
LLC	Low Layer Compatibility (ISDN)
LLC	Logical Link Control
LLU	Local Loop Unbundling (see also ULL)
LMDS	Local Multipoint Distribution System
LMF	Language Media Format
LMI	Local Management Interface
LMOS	Loop Maintenance Operations System
LMR	Land Mobile Radio
LMS	Location and Monitoring Service
LMSS	Land Mobile Satellite Service
LMT	Local Maintenance Terminal
LNA	Launch Numerical Aperture
LNA	Low Noise Amplifier
LNB	Low Noise Block
LNM	LAN Network Manager
LNP	Local Number Portability
LNR	Last Number Redial
LO	Local Oscillator
LOB	Line Of Bearing
LOF	Lowest Operating Frequency
LORAN	Long-Range Radio Aid To Navigation System
LOS	Line Of Sight
LOS	Loss Of Signal
LP	Linear Programming
LP	Linearly Polarised
LP	Linking Protection
LP	Log-Periodic
LPA	Linear Power Amplifier
LPC	Linear Predictive Coding
LPD	Low Power Device
LPD	Low Probability Of Detection
LPI	Low Probability of Intercept
LQA	Link Quality Analysis
LRAIC	Long Run Average Incremental Costs
LRC	Longitudinal Redundancy Check
LRIC	Long Run Incremental Costs
LS	Loop-Start Signalling
LSB	Lower Sideband, Least Significant Bit
LSI	Large Scale Integrated or Integration
LSI	Line Status Indication
LSL	Link Support Layer
LSPSD	Low-Speed Packet Switched Data
LSRP	Link-State Routing Protocol
LST	Loudspeaking Telephone
LT	Line Termination
LTA	Lesotho Telecommunications Authority
LTC	Line Traffic Coordinator
LTE	Line Terminating Equipment
LTU	Line Termination Unit
LU	Logical Unit (IBM)
LUF	Lowest Usable Frequency
LULT	Line-Unit-Line Termination
LUNI	LAN Emulation User-to-Network Interface
LUNT	Line-Unit-Network Termination
LV	Low Voltage
LVD	Low Voltage Directive (European Union)
M
M/W	Microwave
MA	Medium Adaptor
MAC	Media Access Control
MAC	Medium Access Control (protocol layering context)
MAC	Move, Add, and Change
MAC	Multiplexed Analogue Components
MAC	Standards Multiplex of Analogue Components (time division multiplex technique for TV/HDTV transmission)
MACRA	Malawi Communications Regulatory Authority
MAE	Metropolitan Access Exchange
MAE	Metropolitan Area Exchange
MAF	Management Application Function (TMN)
MAI	Mobile Allocation Index
MAN	Metropolitan Area Networks
MAP	Manufacturing Automation Protocol
MAP	Mobile Application Part
MAP/TOP	Manufacturing Automation Protocol/Technical and Office Protocol
MAPI	Messaging Applications Programming Interface (Microsoft)
MAPS	Maps Application Provisioning System
MAR	Memory Address Register
MARS	Multicast Address Resolution Server
Maser	Microwave Amplification by the Stimulated Emission of Radiation
MAT	Maintenance Acceptance Test
MATSE	Mobile Automatic Telephone System - Europe
MAU	Maximum Attachment Unit
MAU	Medium Access Unit
MAU	Medium Attachment Unit (Ethernet)
MAU	Multistation Access Unit
MBFT	Multipoint Binary Transfer File
M-Bone	Multimedia Backbone
Mbps	Megabits per second
MBR	Maritime Business Radio
MBS	Mobile Broadband System
MC	Management Centre
MC	Message Centre
MCA	Malta Communications Authority
MCA	Micro Channel Architecture
MCC	Maintenance Control Circuit
MCC	Mobile Country Code
MCCOI	Multimedia Communications Community of Interest
MCDV	Maximum Cell Delay Variation
MCF	Message Communication Functions (TMN)
MCLR	Maximum Cell Loss Ratio
MCM	Multicarrier Modulation
MCMC	Malaysian Communications and Multimedia Commission
MCPC	Multiple Channel Per Carrier
MCPR	Multimedia Communication Processing and Representation
MCR	Minimum Cell Rate (ATM)
MCS	Master Control System
MCS	Multipoint Communication Service
MCT	Model Compatibility Test
MCTD	Maximum Cell Transfer Delay
MCU	Metered Calling Unit
MCU	Multipoint Control Unit
MCVF	Multi-Channel Voice Frequency
MCW	Modulated Continuous Wave
MD	Mediation Device
MDB	Management Database
MDBS	Mobile Database Station
MDF	Main Distribution Frame
MDIS	Mobile Data Intermediate System
MDN	Message Disposition Notification
MDN	Mobile Directory Number
MDNS	Managed Data Network Service
MDR	Memory Data Register
MDS	Moderate Speed Digital Subscriber Line
MDT	Manufacturer’s Delegated Testing
MDT	Mean Downtime
MDTRS	Mobile Digital Trunked Radio Systems
ME	Maintenance Entities
ME	Mobile Equipment
MEA	Modern Equivalent Asset
MEECN	Minimum Essential Emergency Communications Network
MEF	Maintenance Entity Function
MEG	Mobile Experts Group
MEO	Medium Earth Orbit
MEOS	Medium Earth Orbit Satellites
MERS	Most Economical Route Selection
MES	Master Earth Station
MExE	Mobile Station Application Execution Environment
MF	Mediation Function
MF	Medium Frequency
MF	Multi Frequency
MFD	Mode Field Diameter
MFLOPS	Millions of Floating Point Operations Per Second
MFSK	Multiple Frequency-Shift Keying
MG	Master Group
MGW	Media GateWay
MHF	Medium High Frequency
MHRP	Multi Host Routing Protocol
MHS	Message Handling Service
MHS	Message Handling Source
MHS	Message Handling System
MHz	Megahertz
MIB	Management Information Base
MIC	Management Integration Consortium
MIC	Medium Interface Connector
MIC	Microphone
MIC	Microwave Integrated Circuit
MIC	Minimum Ignition Current
MIC	Monolithic Integrated Circuit
MIC	Mutual Interface Chart
MICP	Mobile Internetworking Control Protocol
MID	Message Identifier (ATM SMDS)
MID	Multiplexing Identifier (ATM)
MIDA	Multiple Integrated Digital Access (UK)
MILNET	Military Network (US)
MIL-STD	Military Standard (US)
MIME	Multipurpose Internet Mail Extension
MIN	Mobile ID Number
MIP	Medium Interface Point
MIPS	Millions of Instructions per Second
MIS	Management Information Services
MIS	Management Information System
MIT	Massachusetts Institute of Technology
MIX	Multiservice Interchange
MJPEG	Multi Joint Photography Experts Group
MLC	Multilink Control Field (X25)
MLE	Maximum Likelihood Estimator
MLP	Multilink Protocol (X25)
MLPP	Multilevel Precedence And Preemption
MLS	Mobile Location Services
MLS	Multiple Listing Service
MMB	Milli-Metric Band (ETSI)
MMDS	Multichannel Multipoint Distribution System
MMF	MultiMode Fibre
MMI	Man Machine Interface
MMoIP	Multimedia Mail over IP
MMP	Multichassis Multilink PPP
MMS	Multimedia Message Service
MMSI	Maritime Mobile Service Identities
MNO	Mobile Network Operator
MNP	Mobile Number Portability
MO	Magneto-Optical Modem Modulator/Demodulator
MOC	Mobile Originating Call
MOCVD	Metallo-Organic Chemical Vapour Deposition
MOD	Demodulation
MOD	Model
MOD	Modification
MOD	Modulation
Modem	Modulator-Demodulator
MOH	Music on Hold
MOM	Method of Movements
MOP	Maintenance Operations Protocol
MOS	Mean Opinion Score (voice quality score)
MoU	Memorandum of Understanding
MOU	Minutes of Use
MP	Multiplexing
MP3	MPEG Audio Layer 3
MPC	Multi Frequency Code
MPEG	Motion Pictures Expert Group
MPF	Metallic Path Facility
MPLS	MultiProtocol Label Switching
MPOA	Multiprotocol over ATM
MPP	Multichannel Point-to Point Protocol
MPPP	Multilink Point-to-Point Protocol
MRA	Mutual Recognition Agreement
MRCF	Maximum Rate of Exchange of Frequency
MS	Managed Services
MS	Mobile Station
MSB	Most Significant Bit
MSC	Main Switching Centre
MSC	Mobile Switching Centre
MSDT	Multi-Services Distant Terminal
MSE	MExE Service Environment
MSG	Message
MSI	Mid-Span Interconnection
MSIN	Mobile Station Identification Number
MSISDN	Mobile Subscriber International Subscriber Identity Number
MSISDN	Mobile Station International ISDN
MSK	Minimum Shifting Key
MSN	Microsoft Network
MSO	Mobile Switching Office
MSO	Multiple Service Operator
MSP	Multiplex Section Protection
MSRN	Mobile Station Roaming Number
MSS	Mobile Satellite Systems
MSS	MAN Switching System
MSSHO	Mobile Speed Sensitive Handover
MS-SPRING	Multiplex Section Shared Protection Ring
MST	Multi-Service Terminal
MT	Mobile Termination
MTA	Mail Transport Agent
MTA	Message Transfer Agent
MTBF	Mean Time Between Failures
MTBM	Mean Time Between Maintenance
MTBO	Mean Time Between Outages
MTBPM	Mean Time Between Preventive Maintenance
MTC	Mobile Terminated Call
MTF	Modulation Transfer Function
MTP	Message Transfer Part
MTP	Multicast Transport Protocol
MTS	Message Telecommunications Service
MTS	Message Toll Service
MTS	Message Transfer System
MTSO	Mobile Telephone Switching Office
MTSR	Mean Time to Service Restoral
MTTR	Mean Time to Repair
MTU	Maximum Transmission Unit
MTU	Multi-Tenant Unit
MU	Message Unit
MUF	Maximum Usable Frequency
muldem	Multiplexer/Demultiplexer
MUNDI	Multiplexed Network for Distributive and Interactive Services
MUX	Multiplexer
MUXing	Multiplexing
MVDS	Microwave Video Distribution System
MVDS	Multipoint Video Distribution System
MVIP	Multi Vendor Integration Protocol
MVNO	Mobile Virtual Network Operator
MVPRP	Multivendor Problem Resolution Process
MVS	Multiple Virtual Storage
MWI	Message Waiting Indicator
MWV	Maximum Working Voltage
N
NA	Network Adaptor
NA	Network Aspects
NA	Numerical Aperture
NACD	Network Automatic Call Distribution
NACS	NetWare Asynchronous Communication Services
NACSEM	National Communications Security Emanation Memorandum
NACSIM	National Communications Security Information Memorandum
NADF	North American Directory Forum
NADN	Nearest Active Downstream Neighbour
NAK	Negative Acknowledgement
NAM	Numeric Assignment Module
NAMAS	National Measurement Accreditation Service
N-AMPS	Narrowband Advanced Mobile Phone System
NANOG	North American Network Operator’s Group
NANP	North American Numbering Plan
NANPA	North American Numbering Plan Administration
NAP	Network Access Point (Internet)
NAP	Network Access Provider (US)
NASA	National Aeronautics and Space Administration
NAT	Network Address Translation
NATA	North American Telecommunications Allocation
NAU	Network Addressable Unit
NAUN	Nearest Active Upstream Neighbour
NAVSTAR-GPS	Navigational Satellite Timing and Ranging--Global Positioning System
NB	Notified Body
NBDP	Narrow Band Direct Printing
NBFM	Narrowband Frequency Modulation
NBH	Network Busy Hour
NBMA	NonBroadcast MultiAccess
NBRVF	Narrowband Radio Voice Frequency
NBSV	Narrowband Secure Voice
NC	Network Computer
NCA	National Communications Authority (Ghana)
NCC	Namibian Communications Commission
NCC	Nigerian Communications Commission
NCC	Network Control Centre
NCCF	Network Communication Control Facility
NCCN	Network Charge Change Notice
NCC	New Common Carrier (Japan)
NCO	Numerical Control Oscillator
NCOP	Network Code of Practice
NCP	Network Connection Point
NCP	Network Configuration Process
NCP	Network Control Point
NCP	Network Control Programme
NCS	National Communications System
NCS	Net Control Station
NCSC	National Communications Security Committee
NCTE	Network Channel Terminating Equipment
NDCS	Network Data Control System
NDIS	Network Device Interface Standard
NDS	Network Distribution System
NE	Network Element
NEBS	New Equipment Building Specifications
NECA	National Exchange Carrier Association
NEF	Network Element Function Block
NEMS	Network Element Management Server
NEP	Noise Equivalent Power
NER	Network Efficiency Ratio
NES	Noise Equivalent Signal
NET	Norme Europeenne de Telecommunications
NetBEUI	NetBIOS Extended User Interface
NetBIOS	Network Basic Input/Output System
NETC	National Electronics Test Centre (Ireland)
NETID	Network Identifier
NEXT	Near End Cross Talk
NF	Noise Figure
NGN	Next-Generation Network
NHH	National Communications Authority (Hungary)
NHRP	Next Hop Routing Protocol
NHS	Next Hop Server
NI	Network Interface
NIC	Network Information Centre (Internet Registry)
NIC	Network Interface Card (LAN)
NICC	Network Interoperability Consultative Committee
NICE	Network Information and Control Exchange
NICS	NATO Integrated Communications System
NID	Network Information Database
NID	Network Interface Device
NID	Network Inward Dialling
NII	National Information Infrastructure
NIOD	Network Inward/Outward Dialling
NIS	Network Information Service
N-ISDN	Narrow-band Integrated Services Digital Network (ISDN)
NIST	National Institute of Standards and Technology (US)
NIT	Networking Interworking Tests
NIU	Network Interface Unit
NIUF	North American ISDN Users Forum
NL	Network Layer
NL	Number of Unallocated Channels on Link
NLD	National Long Distance
NLDM	Network Logical Data Manager
NLP	National Level Programme
NLPID	Network Layer Protocol Identifier
NLSP	NetWare Link Services Protocol
NM	Network Management
NM	Network Module
NMC	Network Management Centre
NMDS	Narrow-band Multi-service Delivery System
NML/NMS	Network Management Layer/Network Management Service
NMP	Network Management Protocol
NMR	Nuclear Magnetic Resonance Scanner
NMS	Network Management System
NMSI	National Mobile Station Identification Number
NMT	Nordic Mobile Telephone System
NN	Network Node
NNG	National Number Group
NNI	Network Node Interface (ATM)
NNI	Network-to-Network Interface
NOA	Nature of Address
NOAF	Network Operator Facility
NOC	Network Operations Centre
NOCC	Network Operations Control Centre
NOD	Network Outward Dialling
NORC	Network Operators Research Committee
NOS	Network Operating System
NP	Network Performance
NP	Number Portability
NPA	Numbering Plan Area
NPC	Network Parameter Control (ATM)
NPDU	Network Layer Protocol Data Unit
NPI	Numbering Plan Identification
NPR	Noise Power Ratio
NPT	Norwegian Post and Telecommunications Authority
NRA	National Regulatory Authority
NREN	National Research and Education Network (US)
NRI	Net Radio Interface
NRM	Network Resource Manager
NRM	Normal Response Mode
NRZ	Non-Return-to-Zero
NRZ-M	Non-Return-to-Zero Mark
NRZ-S	Non-Return-to-Zero Space
NS/EP	Telecommunications National Security or Emergency Preparedness Telecommunications
NSA	National Security Agency (US)
NSAP	Network Service Access Point
NSAPA	Network Service Access Point Address
NSC	Network Service Centre
NSF	National Science Foundation (US)
NSOs	National Standards Organisations
NSP	Network Service Provider
NSP	Native Signal Processing
NSP	Network Service Protocol
NSS	Network Switching Sub-System (GSM)
NSS	Network Subsystem
NSSG	Network Solutions and Service Group
NSTAC	National Security Telecommunications Advisory Committee (US)
NT	Network Termination (ISDN)
NT	New Technology
NTA	Nepal Telecommunications Authority
NTC	National Telecommunications Commission (Philippines)
NTCN	National Telecommunications Coordinating Network
NTE	Network Terminating Equipment
NTI	Network Terminating Interface
NTMS	National Telecommunications Management Structure
NTN	Network Terminal Number
NTO	Network Terminal Option
NTP	Network Termination Point
NTP	Network Time Protocol
NTRA	National Telecommunications Regulatory Authority of Egypt
NTRC	National Telecommunications Regulatory Commission (St Lucia)
NTRC	National Telecommunications Regulatory Commission (St Vincent and the Grenadines)
NTS	Number Translation Services
NTSA	Networking Technical Support Alliance
NTSC	National Television Standards Committee
NTT	Nippon Telegraph & Telephone (Japan)
NTTA	Network Termination and Testing Apparatus
NTU	Network Termination Unit
NVRAM	NonVolatile RAM
NVT ASCII	Network Virtual Terminal ASCII Nailed Line
NXX	Network Numbering Exchange
O
O&M	Operations and Maintenance
OA&M	Operations, Administration and Maintenance
OAC	Operator Assisted Calls
OAM&P	Operations, Administration, Maintenance and Provisioning
OB	Outside Broadcast
OBC	Out-of-Band Connection
OBM	Optimised Bandwidth Management
OC	Operations Centre
OC	Optical Carrier (SONET)
OCC	Other Common Carriers
OCCA	Open Cooperative Computing Architecture
OCHC	Operator Call Handling Centre
OCR	Optical Character Recognition
OCR	Optical Character Reader
OCTPR	Office of the Commissioner of Telecommunications & Postal Regulation (Cyprus)
OCU	Orderwire Control Unit
OD	Optical Density
ODA	Open Document Architecture
ODBC	Open Database Connectivity
ODF	Optical Distribution Frame
ODI	Open Data-Link Interface
ODIF	Open Document Interchange Format
ODS	Operational Data Store
ODSI	Open Directory Services Interface
OECD	Organisation for Economic Cooperation and Development
OEIC	Opto-Electronic Integrated Circuit
OEM	Original Equipment Manufacturer
OFC	Optical Fibre, Conductive
OFCOM	Office Fédéral de la Communication (Switzerland - see also BAKOM)
OFCOM	Office of Communications (UK)
OFCP	Optical Fibre, Conductive, Plenum
OFCR	Optical Fibre, Conductive, Riser
OFDM	Orthogonal Frequency Division Multiplex
OFM	Optical Frequency Multiplexing
OFN	Optical Fibre, Nonconductive
OFNP	Optical Fibre, Nonconductive, Plenum
OFNR	Optical Fibre, Nonconductive, Riser
OHD	On Hook Dialling
OID	Object Identifier
OIM	OSI Internet Management
OLAP	Online Analytical Processing
OLC	Optical Loop Carrier
OLI	Optical Line Inlet
OLO	Other Licensed Operator
OLO	Optical Line Outlet
OLR	Overall Loudness Rating
OLTE	Optical Line Terminating Equipment
OMA	Object Management Architecture
OMA	Open Mobile Alliance
OMC	Operations and Maintenance Centre
OME	Operator Mobile Exchange
OMERT	Office Malagasy d’Études et de Régulation des Télécommunications (Madagascar)
OMF	Object Management Framework
OMG	Object Management Group
OMP	Open Market Provision
OMT	Operations and Maintenance Terminal
ONA	Open Network Architecture
ONAL	Off-Network Access Line
ONC	Open Network Computing
ONMS	Open Network Management System
ONP	Open Network Provision
ONPCCP	ONP Consultative and Co-ordination Platform
ONU	Optical Network Unit
OOE	Organisation Outside ETSI
OOP	Object-Oriented Programming
OPEX	Operating Expanditures
opm	Operations Per Minute
OPMODEL	Operations Model
OPSEC	Operations Security
OPTA	Onafhankelijke Post en Telecommunicatie Authoriteit (NRA of the Netherlands)
OPX	Off Premises Extension
OQPSK	Orthagonal Quadrature PSK
OR	Off-Route Aeronautical Mobile Service
ORB	Object Request Broker
ORDR	Optical Time Domain Reflectometry
ORM	Optically Remote Switching Module
OS	Operations Systems
OSA	Open Service Architecture
OSF	Open Software Foundation
OSF	Operations Systems Function Block
OSHA	Occupational Safety and Health Administration (US)
OSI	Open Switching Interval
OSI	Open Systems Interconnection (ISO interface specifications)
OSI/NMF	OSI Network Management Forum
OSINET	OSI Network
OSIPTEL	Organismo Supervisor de Inversión Privada en Telecomunicaciones (Peru)
OSI-RM	Open Systems Interconnection--Reference Model
OSIRM	Open Systems Interconnection Reference Model (ISO ITU-T)
OSITOP	Open Systems Interconnection/Technical and Office Protocol
OSP	Outside Plant
OSPF	Open Shortest Path First
OSRI	Originating Stations Routing Indicator
OSS	One Stop Shopping
OSS	Operation Support Systems
OSSN	Originating Stations Serial Number
OTA	Over-the-Air
OTAM	Over-the-Air Management of Automated HF Network Nodes
OTAR	Over-the-Air Rekeying
OTDR	Optical Time Domain Reflectometer
OTE	Operator Tandem Exchange
OTRT	Office Tchadien de Régulation des Télécoms (Chad)
OUI	Organisational Unique Identifier
OUR	Office of Utilities Regulation (Jamaica)
OW	Orderwire
P
p/a r	Peak-to-Average Ratio
P/P	Point-to-Point
P2P	Person-to-Person
PABX	Private Automatic Branch Exchange
PAC	Programme Advisory Committee (ETSI)
PACE	Priority Access Control Enabled
PACS	Personal Access Communications System
PACT	Public Access Cordless Telephony
PAD	Packet Assembler/Disassembler
PAL	Phase Alternation by Line (colour TV standard)
PAL-M	Phase Alternation by Line - Modified
PAM	Pulse Amplitude Modulation
PAMA	Pulse-Address Multiple Access
PAMR	Public Access Mobile Radio
PAMS	Perceptual Analysis / Measurement System (ITU-based standard P.800)
PAN	Personal Area Network
PAP	Password Authentication Protocol
PAR	Performance Analysis And Review
PARAMP	Parametric Amplifier
PAT	Port Address Translation
PAX	Private Automatic Exchange
PBER	Pseudo-Bit-Error-Ratio
PBP	Packet Burst Protocol
PBX	Private Branch Exchange
PC	Carrier Power (of a radio transmitter)
PC	Path Control
PC	Printed Circuit
PCA	Position of Closed Approach
PCB	Power Circuit Breaker
PCB	Printed Circuit Board
PCB	Process Control Block
PCB	Public Call Box (payphone)
PCC	Prepaid Calling Card
PCC	Primary Cross Connect
PCH	Paging Channel
PCI	Peripheral Component Interconnect
PCI	Pre-Connection Inspection
PCI	Programmable Communication Interface
PCI	Protocol Control Information
PCIA	Personal Communications Industry Association
PCM	Plug Compatible Module
PCM	Process Control Module
PCM	Pulse Code Modulation
PCMCIA	Personal Computer Memory Card Industry Association
PCN	Personal Communications Network
PCN	Personal Communications Number
PCO	Public Call Office
PCR	Peak Cell Rate (ATM)
PCS	Personal Communication Services
PCS	Personal Communication Space
PCS	Personal Communication System
PCS	Plastic-Clad Silica (fibre)
PCS	Port Concentrator Switch
PCS1900	Personal Communications System 1900 MHz
PCSN	Private Circuit Switching Network
PCSR	Parallel Channels Signalling Rate
PCT	Private Communication Technology
PCU	Premises Control Unit
PDA	Personal Digital Assistant
PDC	Personal Digital Cellular
PDD	Post Dial Delay
PDE	Positioning Determination Entity
PDF	Portable Document Format
PDH	Plesiochronous Digital Hierarchy
PDM	Pulse-Duration Modulation
PDN	Packet Data Network
PDN	Public Data Network
PDS	Power Distribution System
PDS	Protected Distribution System
PDT	Programmable Data Terminal
PDU	Protocol Data Unit
PE	Phase-Encoded
PE	Public Enquiry
PEAN	Pan-European ATM Network
PED	Portable Electronic Devices
PEM	Privacy Enhanced Mail
PEP	Peak Envelope Power (of a radio transmitter)
PESQ	Perceptual Evaluation of Speech Quality (ITU-standard P.862)
PET	Planning Exercise in Telecommunications technologies (forerunner of RACE)
PF, pf	Picofarad
PF	Power Factor
PFD	Power Flux Density
PFM	Pulse-Frequency Modulation
PGT-10	The Conference of European Postal and Telecommunications Administrations’ general tariff principles study group.
PH	Personal Handyphone System
PHY	Physical Layer
PHY	Physical Sublayer
PI	Protection Interval
PI	Programming Infrastructure
PIC	Plastic Insulated Cable
PIC	Primary Interexchange Carrier (US)
PICS	Protocol Implementation Conformance Statement
PIM	Personal Information Manager
PIM	Protocol Independent Multicast
PIM DM	PIM Dense Mode
PIM SM	PIM Sparse Mode
PIN	Personal Identification Number
PIN	Positive-Intrinsic-Negative
ping	Packet Internet Groper
PINX	Private Telecommunications Network Exchange
PITCOM	Parliamentary Information Technology Committee (UK)
PIV	Peak Inverse Voltage
PIXIT	Protocol Implementation Extra Information for Testing
PKC	Public Key Cryptology
PKI	Public Key Infrastructure
PL	Private Line
PL	Project Line
PLAR	Private Line, Automatic Ringdown
PLC	Power Line Communications
PLC	Programming Logic Controller
PLCP	Physical Layer Convergence Procedure
PLIM	Physical Layer Interface Module
PLISO	Plesisochronous
PLL	Phase-Locked Loop
PLMN	Public Land Mobile Network
PLN	Private Line Network
PLP	Packet Layer Protocol (X25)
PLR	Pulse Link Repeater
PLS	Physical Signalling Sublayer
PLSP	PNNI Link State Packets
PLU	Primary Logical Unit
PM	Mean Power
PM	Phase Modulation
PM	Physical Medium
PM	Polarisation-Maintaining (optical fibre)
PM	Preventive Maintenance
PM	Pulse Modulation
PMA	Physical Medium Attachment
PMBS	Packet Mode Bearer Service
PMBX	Private Manual Exchange System
PMD	Physical Medium Dependent (FDDI)
PMN	Public Mobile Network
PMO	Programme Management Office
PMR	Private Mobile Radio
PNNI	Private Network Node Interface (ATM)
PNO	Public Network Operator
PnP	Plug-and-Play
PNT	Private Network Termination
POC	Point of Connection
POD	Programmable Option Devices
POET	Packet Over E3/T3
POI	Point Of Interconnect
PON	Passive Optical Network
POP	Point of Presence
POP	Post Office Protocol
PoS	Point Of Sale
POSI	Promotion of OSI
POSIT	Profiles for Open Systems Interworking Technologies
POSIX	Portable Operating System Interface for Computer Environments
POSTEL	Directorate General of Posts and Telecommunications (Indonesia)
POTRAZ	Postal and Telecommunications Regulatory Authority of Zimbabwe
POTS	Plain Old Telephone Service
P-P	Peak-to-Peak
PP	Polarisation-Preserving (optical fibre)
PPC	Pay-Per-Call
PPCC	Prepaid Calling Card
PPM	Pulse-Position Modulation
PPP	Point-to-Point Protocol
PPS	Precise Positioning Service
PPS	Pulses per Second
PPV	Pay-per-View
PQA	Product Quality Assurance
PR	Pulse Rate
PRBS	Pseudo Random Bits Sequence
PRD	Programme Reference Document
PRF	Pulse-Repetition Frequency
PRI	Primary Rate Interface (ISDN)
PRM	Pulse-Rate Modulation
PRMD	Private Management Domain
PRN	Pseudo Random Noise
PROM	Programmable Read-Only Memory
PRP	Primary Routing Point
PRR	Pulse Repetition Rate
PRS	Premium Rate Service
PRSIG	Pacific Rim SMDS Interest Group
PRSL	Primary Area Switch Locator
PS	Packet Switched
PS	Paging Systems
PS	Permanent Signal
PS	Power Supply
PSB	Public Service Board
PSC	Public Service Commission (US)
PSD	Power Spectral Density
PSDN	Packet Switched Data Network
PSE	Packet Switching Exchange
PSK	Phase Shift Keying
PSN	Packet-Switched Network
PSN	People with Special Needs
PSN	Public Switched Network
PSP	Personal Software Products
PSPDN	Packet Switched Public Data Network
PSQM	Perceptual Speech Quality Measurement (ITU-standard P.861)
PST	Plug-and-Socket Terminated
PSTN	Public Switched Telecommunications Network
PSU	Power Supply Unit
PT	Payload Type
PTA	Pakistan Telecommunication Authority
PTA	Post and Telecom Administration (Iceland)
PTD	Post and Telegraph Department (Thailand)
PTF	Patch And Test Facility
PTI	Packet Type Identifier (X25)
PTI	Payload Type Identifier (ATM)
PTM	Packet Transport Mode
PTM	Plesiochronous Transmission
PTM	Pulse-Time Modulation
PTN	Public Telecommunication Network
PTNX	Private Telecommunications Network Exchange
PTO	Public Telecommunication Operator
PTS	National Post and Telecom Agency (Sweden)
PTS	Public Telecommunications System
PTT	Post, Telephone and Telegraph
PTT	Push-to-Talk
PTTC	Paper Tape Transmission Code
PTTI	Precise Time And Time Interval
PU	Pick-Up
PU	Power Unit
PU	Physical Unit
PUC	Public Utilities Commission (US)
PURA	Public Utility Regulatory Authority (Gambia)
PVC	Permanent Virtual Circuits
PVC	Polyvinyl Chloride
PVN	Private Virtual Network
PVP	Permanent Virtual Paths
PW	Private Wire
PWB	Printed Wiring Board
PWM	Pulse-Width Modulation
PWT	Personal Wireless Telephone
PX	Private Exchange
PXML	Private Exchange Master List
Q
Q3	Network Management Interface (ITU-T)
QA	Quality Assurance
QA	Q-Adapter (TMN)
QAFQ	Adapter Block (TMN)
QAIG	Signalling in Q-Point (private ISDN networks)
QAM	Quadrature Amplitude Modulation
Q-bit	Qualified Data Bit (X25)
QC	Quality Control
QCIF	Quarter CIF
QI	Quality Index
QLLC	Qualified Logical Link Control
QMR	Qualitative Material Requirement
QoS	Quality of Service
QPD	Qualified Program Document
QPL	Qualified Product List
QPSK	Quadrature Phase Shift Key
QPSX	Queued Packet Synchronous Exchange
QRC	Quick Reaction Capability
QRS	Quasi-Random Signal
QRSS	Quasi-Random Signal Sequence
QSIG	Unified international corporate network signalling standard
QSTAG	Quadripartite Standardisation Agreement
QUICK	Trenching Quicker Underground Integrated Cabling and Networking
R
R	Receiver
R	Route Service
R&D	Research & Development
R/T	Real Time
RA	Remote Access
RAC	Relay Access Card
RACE	Research and Development in Advanced Communications Technologies in Europe
RACH	Random Access Channel
RADHAZ	Electromagnetic Radiation Hazards
RADINT	Radar Intelligence
RADIUS	Remote Dial-In User Service
RADSL	Rate Adaptive Digital Subscriber Line
RAIM	Receiver Autonomous Integrity
RAM	Random Access Memory
RAM	Reliability, Availability, And Maintainability
RAN	Radio Access Network
RARE	Réseaux Associés pour la Recherche Européenne
RARP	Reverse Address Resolution Protocol
RAS	Remote Access Server (Remote LAN)
RATT	Radio Teletypewriter System
RBBS	Residential Broadband Service
RBES	Rule-Based Expert Systems
RBOC	Regional Bell Operating Companies (US)
RC	Rate Centre
RC	Reflection Coefficient
RC	Reference Configuration
RC	Repeating Coil
RC	Resource Controller
RCC	Radio Common Carrier (US)
RCC	Reverse Control Channel
RCE	Remote Channel Extenders
RCF	Routing Control Field
RCO	RACE Central Office
RCP	Remote Copy Protocol
RCU	Remote Control Unit
RCU	Remote Concentrator Unit
RCVR	Receiver
RD	Routing Domain (ATM ISO)
RD&E	Research Development and Engineering
RD&T	Research Development and Technology
RDBMS	Relational Database Management System
RDF	Route Designator Field
RDI	Remote Defect Identification
RDP	RACE Definition
RDS	Radio Data Signal/System
RDSS	Radio Determination Satellite Service
RDTD	Restricted Differential Time Delay
RegTP	Regulierungsbehörde für Telekommunikation und Post (German NRA)
REM	Ring Error Monitor
REN	Ringer Equivalent Number
REP	Repeat
RES	Radio Equipment and Systems
RESP	Response
RET	Returning
RF	Radio Frequencies
RFA	Random Fixed Access
RFH	Remote Frame Handler (ISDN)
RFI	Radio Frequency Interference
RFS	Ready for Service
RG	Research Group
RG	Ring Ground
RH	Relative Humidity
RHR	Radio Horizon Range
RI	Routing Indicator
RIC	RACE Industrial Consortium
RIF	Routing Information Field (Source Routing)
RII	Routing Information Indicator (Source Routing)
RIM	Radio Identity Model
RIM	Receiver Intermodulation
RIM	Request Initialisation Mode (HDLC)
RIO	Reference Interconnection Offer
RIP	Routing Information Protocol
RISC	Reduced Instruction Set Computing
RISE	Retrieval and Interchange of Standards in Europe
RJ	Registered Jack
RJE	Remote Job Entry
RLM	Redundant Link Manager
RLR	Receive Loudness Rating
RLSD	Receive Line Signal Detector
RM	Resource Management
RMC	RACE Management Committee
RMON	Remote Network Monitoring
RMU	Resource Management Units
RNC	Radio Network Controller
RNS	Radio Network Subsystem
RO	Read Only / Receive Only
ROA	Recognised Operating Agency
ROC	Required Operational Capability
ROCE	Return on Capital Employed
ROH	Receiver Off-Hook
ROI	Return On Investment
ROM	Read-Only Memory
ROMP	Remote Operations Microprocessor
RoR	Rate of Return
ROSE	Remote Operation Service Element (Application Layer)
RP	Registration Point
RPC	Remote Procedure Call
RPF	Reverse Path Forwarding
RPI	Retail Price Index
RPS	Ring Parameter Server
RQ	Repeat-Request
RR	Radio Regulations (ITU)
RR	Register Recall (Timed Break)
RR	Relative Rate
RR	Repetition Rate
RRB	Radio Regulations Board
RS	Remote Station
RSA	Rivest, Shamir, and Adelman (public-key cryptographic system)
RSCV	Route Selection Control Vector
RSH	Remote Shell Protocol
RSL	Received Signal Level
RSM	Remote Switching Module
RSP	Route/Switch Processor
RSRB	Remote Source-Route Bridging
RSS	Radio Subsystem
RSS	Remote Switch Subsystem
RSVP	Resource Reservation Protocol
RT	Real Time
RT	Remote Terminal
RT	Ringback Tone
RT	Routing Type
RTA	Remote Trunk Arrangement
RTC/RTS	Regional Tele Centre/Regional Tele Server
RTCP	Real-Time Control Protocol
RTCP	RTP Control Protocol
RTF	Rich Text Format
RTP	Rapid Transport Protocol
RTP	Real-Time Transport Protocol
RTP	Routing Table Protocol
RTS	Request to Send
RTSC	Regional Telematic Service Centre
RTSE	Remote Transfer Service Element (Application Layer)
RTSP	Real Time Streaming Protocol
RTTE	Radio and Telecommunication Terminal Equipment (also R&TTE)
RTTE-CA	Radio and Telecommunication Terminal Equipment Compliance Association
RTTY	Radio Teletypewriter
RTU	Radio Termination Unit
RTU	Remote Telemetry Units
RTU	Right to Use
Rt-VBR	Real Time Variable Bit Rate
RTX	Request to Transmit
RU	Request/Response Unit
RUDP	Reliable User Data Protocol
RUO	Reference Unbundling Offer
RVA	Reactive Volt-Ampere
RVWG	Reliability and Vulnerability Working Group
RWI	Radio and Wire Integration
RWT	Right When Tested
RX	Receiver
Rx	Reception
RXLEV	Received Signal Level
RXQUAL	Received Signal Quality
RZ	Return-to-Zero
S
S x S	Step-by-Step
S/H	Sample and Hold
S/N	Signal to Noise Ratio
S/R	Send and Receive
SA	Selective Availability
SA	Source Address
SA	Subscribers’ Apparatus
SA	Switched Access
SAA	Systems Application Architecture (IBM)
SAACH	Slow Associated Control Channel
SAAL	Signalling ATM Adaptation Layer (ATM)
SABM	Set Asynchronous Balanced Mode (HDLC)
SABME	Set Asynchronous Balanced Mode Extended (HDLC)
SAC	Service Access Code
SAC	Single-Attached Concentrator
SAC	Stand-Alone Costs
SAER	Service and Equipment Record
SAM	System Administration Module
SAP	Service Advertising Protocol
SAP	Source Access Point
SAPI	Service Access Point Identifier (LAPD)
SAR	Segmentation and Re-assembly (ATM)
SARM	Set Asynchronous Response Mode (HDLC)
SAS	Simple Attachment Scheme
SAS	Single Attachment Station
SAS	Statically Assigned Socket
SAT	SIM Application Toolkit
SATAN	System Administrator Tool for Analysing Networks
SB	Synchronisation Burst
SBSVC	Selective Broadcast Signalling Virtual Channel (B- ISDN)
SC	Self-Contained
SC	Signalling Converter
SC	Switching Centre
SC	Standards Committee (ISO)
SCA	System Communication Architecture
SCADA	Supervisory Control and Data
SCC	Specialised Common Carrier
SCCP	Signalling Connection Control Part
SCDC	Single Commutation Direct Current
SCE	Service Creation Environment
SCEF	Service Creation Environment Function
SCF	Service Control Function
SCH	Synchronisation Channel
SCP	Service Control Point
SCP	Session Control Protocol
SCPC	Single Channel per Carrier
SCR	Semiconductor-Controlled Rectifier
SCR	Silicon-Controlled Rectifier
SCR	Sustained Cell Rate (ATM)
SCRA	Small Call Routing Apparatus
SCSI	Small Computer Systems Interface
SCSR	Single Channel Signalling Rate
SCTE	Society of Cable Telecommunications Engineers
SCVF	Single Channel Voice Frequency
S-DAB	Satellite Digital Audio Broadcasting
SDCCH	Standalone Dedicated Control Channel
SDF	Specialised Database Functions (TMN)
SDH	Synchronous Digital Hierarchy (ITU-T)
SDK	Software Development Kit
SDLC	Synchronous Data Link Control
SDLS	Single-Line Digital Subscriber Line
SDM	Space Division Multiplexing
SDN	Software-Defined Network (AT&T)
SDR	Software Defined Radio
SDSL	Single-Line Digital Subscriber Line
SDSU	SMDS Data Service Unit
SDU	Service Data Unit
SE	Support Entity
SE	Support Equipment
SECAM	Séquentiel à Mémoire (French colour TV standard)
SECORD	Secure Voice Cord Board
SECTEL	Secure Telephone
SEF	Support Entity Function
SEMKO	Swedish Institute for Testing and Approval of Electrical Equipment
SES	Satellite Earth Stations
SET	Secure Electronic Transaction
SETAMS	Systems Engineering, Technical Assistance, and Management Services
SEVAS	Secure Voice Access System
SEWG	Spectrum Engineering Working Group of CEPT ERC
S-F	Store-and-Forward
SF	Single-Frequency
SF	Super Frame
SFS	Single-Frequency Signalling
SFS	Start of Frame Sequence (LAN)
SG	Study Group (ITU-T)
SG	Supergroup
SGCP	Simple Gateway Control Protocol
SGDF	Supergroup Distribution Frame
SGML	Standard Generalised Markup Language
SGMP	Simple Gateway Monitoring Protocol
SGNT	Special Grade Network Trunk
SGSN	Serving GPRS Support Node
SHARES	Shared Resources HF Radio Programme
SHF	Super High Frequency
S-HTTP	Service Hypertext Transport Protocol
SI	International System of Units
SI	Statutory Instrument (Ireland and UK)
SIB	Service Independent Building Block
SID	Sudden Ionospheric Disturbance
SID	System ID Number
SIF	Signalling Information Field
SIG	SMD Interest Group
SIG	Special Interest Group
SIGET	Superintendencia General de Electricidad y Telecomunicaciones (El Salvador)
SIM	Subscriber Identity Module
SIMD	Single Instruction Stream Multiple Data Stream
SINAD	Signal-Plus-Noise-Plus-Distortion to Noise-Plus- Distortion Ratio
SIN	Suppliers Information Notes (British Telecom)
SIO	Scientific and Industrial Organisations (ITU-T)
SIP	Session Initiation Protocol (IETF)
SIP	SMDS Interface Protocol
SIR	Sustained Information Rate (SMDS)
SIT	Superintendencia de Telecomunicaciones (Guatemala)
SITTEL	Superintendencia de Telecomunicaciones (Bolivia)
SITA	Society of International Aeronautical Telecommunications
SITS	Special Investigation Test Schedule (UK)
SJF	Shortest Job First
SKU	Stock-Keeping Unit
SLA	Service Level Agreement
SLC	Subscriber Loop Carrier
SLEE	Service Logic Execution Environment
SLI	Service Logic Interpreter
SLIC	Subscriber Loop Interface Circuit
SLIP	Serial Line Internet Protocol (IETF)
SLM	Service Level Management
SLP	Service Logic Program
SLR	Send Loudness Rating
SLSA	Single Line Switching Apparatus
SLU	Sub-Loop Unbundling
SLUO	Sub-Loop Unbundling Operator
SMA	Service Management Architecture
SMAF	Service Management Agent Function (TMN)
SMAP	System Management Application Part
SMART	Strategy for Mobile Advanced Radio Telecommunications (initiative of DG XIII/D)
SMATV	Satellite Master Antenna Television
SMB	Server Message Block
SMDR	Station Message Detail Recording
SMDS	Switched Multimegabit Data Service (Bellcore)
SME	Small and Medium Size Business Enterprise
SMF	Service Management Function (TMN)
SMG	Special Mobile Group
SMG	Supermastergroup
SMI	Structure of Management Information
SMIP	Strategic Management Information Plan
SML/SMS	Service Management Layer/Service Management Service
SMP	Significant Market Power
SMP	Simple Management Protocol
SMP	Switching Module Processor
SMP	Symmetric Multiprocessing
SMR	Specialised Mobile Radio
SMRP	Simple Multicast Routing Protocol
SMS	Satellite Multiservice System
SMS	Service Management System
SMS	Short Message Service
SMSC	Short Message Service Centre
SMT	Station Management
SMT	Surface Mounting Technology
SMTA	Single-Line Multi-Extension Telephone Apparatus
SMTP	Simple Mail Transfer Protocol
SN	Sequence Number (ATM)
SN	Service Node
SN	Station Number
SN	Subscriber Number
SN	Switching Network
SNA	Special Network Access
SNA	Systems Network Architecture (IBM)
SNAP	Subnetwork Access Protocol
SNCP	Sub-Network Connection Protection
SNG	Satellite News Gathering
SNI	Subscriber Network Interface (SMDS)
SNMP	Simple Network Management Protocol
SNP	Sequence Number Packet (NetWare)
SNP	Sequence Number Protection
SNPA	Subnetwork Point of Attachment
SNR	Signal to Noise Ratio
SNRM	Set Normal Response Mode (HDLC)
SNRME	Set Normal Response Mode Extended (HDLC)
SO	Switching Office
SOGIT/SOG- ITS	Senior Officials Group for Information Technology Standards
SOGT	Senior Officials Group for Telecommunications
SOM	Start of Message
Sonar	Sound Navigation and Ranging
SONET	Synchronous Optical Network
SOP	Standard Operating Procedure
SOR	Start of Record
SOW	Statement of Work
SP	Service Provider
SP	Signalling Point
SPAG	Standards Promotion and Application Group
SPARC	Scalable Performance Architecture
SPCS	Satellite Personal Communication Services
SPDU	Session Protocol Data Unit
SPF	Shortest Path First
SPID	Service Profile Identifier (ISDN)
SPM	Space Switch Module
SPM	Subscriber Private Meter
SPOC	Single Point of Contact
SPP	Sequenced Packet Protocol
SPRK	Public Utilities Commission (Latvia)
SPS	Signalling Protocols and Switching
SPS	Standard Postioning Service
SPTN	Single Protocol Transport Network
SQE	Signal Quality Error
SQL	Structured Query Language
SR/TLB	Source-Route Translational Bridging
SRAM	Static Random Access Memory (RAM)
SRB	Source-Route Bridging
SREJ	Selective Reject (HDLC)
SRF	Specialised Resources Function (TMN)
SRI	SIP Relay Interface (SMDS)
SRIC	Short Run Incremental Costing
SRNC	Serving Radio Network Controller
SRP	Specialised Resource Point (IN)
SRT	Source-Route Transparent Bridging
SRT	Source Routing Transparent
SRTP	Sequenced Routing Table Protocol
SRTS	Synchronous Residual Time Stamp
SRTT	Satellite Radio Transmission Technologies
SS	Spread Spectrum
SS	Switching System
SS	Supplementary Service
SS6	Signalling System No. 6
SS7	Signalling System No. 7
SSAP	Source Service Access Point
SSB	Service Selection Barring
SSB	Single Side Band
SSBSC	Single Sideband Suppressed Carrier
SSF	Service Switching Function
SSH	Secure Shell Encryption
SSL	Signal Station Location
SSM	Single Segment Message (DQDB SMDS)
SSN	Station Serial Number
SSP	Service Switching Point
SSP	Switch-to-Switch Protocol
SSR	Solid-State Relay
SSS	Subscriber Switching Subsystem
SSSO	Specialised Satellite Services Operator
SST	Spread Spectrum Technology
SST	Synchronous Service Transport
SSUPS	Solid-State Uninterruptible Power System
ST	Signalling Terminal
STAG	Security Techniques Advisory Group (ETSI)
STAX	Standardisation Reference Database
STBX	Set Top Box
STD	Subscriber Trunk Dialling
STD	Synchronous Time Division
STDM	Statistical Time Division Multiplexing
STE	Signalling Terminal Equipment
STE	Spanning-Tree Explorer (LAN)
STEM	Strategic Telecommunication Evaluation Model
STFS	Standard Time and Frequency Signal
STL	Standard Telegraph Level
STL	Studio-to-Transmitter Link
STM	Synchronous Transfer Mode
STM	Synchronous Transport Module (SDH)
STMR	Sidetone Masked Loudness Rating
STP	Shielded Twisted-Pair
STP	Signalling Transfer Point
STP	Standard Temperature and Pressure
STS	Synchronous Transport Signal (SONET)
STU	Secure Telephone Unit
STX	Start of Transmission
SUBT	Subscriber Terminal
SUBTEL	Subsecretaría de Telecomunicaciones (Chile)
SVC	Signalling Virtual Channel (ATM)
SVC	Switched Virtual Circuit (Packet Switching)
SW	Software
SWG	Standard Wire Gauge
SWR	Standing Wave Ratio
SX	Simplex Signalling
SXS	Step-by-Step Switching System
SYNTRAN	Synchronous Transmission
SYSGEN	System Generation
T
TA	Terminal Adapter (ISDN)
TABS	Telemetry Asynchronous Block Serial
TAC	Terminal Access Controller
TACACS	Terminal Access Controller Access Control System
TACS	Total Access Communications Systems
TADIL	Tactical Data Information Link
TADS	Teletypewriter Automatic Dispatch System
TADSS	Tactical Automatic Digital Switching System
TAG	Technical Advisory Group
TAM	Telecommunications Authority of Maldives
TAP	Transfer Account Procedure
TAP	Transmission Access Point
TAPI	Telephony API
TARM	Telephone Answering and Recording Machine
TAS	Suriname Telecommunications Authority
TASI	Time Assigned Speech Interpolation
TAT	Trans-Atlantic Telecommunication (cable)
TAXI 4B/5B	Transparent Asynchronous Transmitter/Receiver Interface 4-byte/5-byte
TB	Technical Body (ETSI)
TB	Time Break
TB	Transparent Bridging
TBB	Trans-National Broadband Backbone
Tbps	Terabit Per Second
TBR	Technical Basis for Regulation (ETSI)
TBR	Time Break Recall
TC	Toll Centre
TC	Transmission Control
TC	Transmission Convergence
TC	Transport Connection
TCA	Time of Closest Approach
TCAM	Telecommunications Access Method (SNA)
TCAP	Transaction Capabilities Application Part
T-Carrier	Trunk Carrier
TCC	Telecommunications Centre
TCC	Terminating Call Control
TCCF	Tactical Communications Control Facility
TCF	Technical Construction File (EU R&TTE)
TCF	Technical Control Facility
TCH	Traffic Channel
TCIF	Telecommunications Industry Forum
TCL	Interface Tool Command Line Interface
TCM	Time Compression Multiplexing
TCP	Transport Control Protocol
TCP/IP	Transmission Control Protocol /Internet Protocol (IETF)
TCRA	Tanzania Communications Regulatory Authority
TCRL	Test Case Reference List
TCS	Trusted Computer System
TCU	Telecommunications Control Unit (SNA)
TCU	Trunk Coupling Unit
TCVXO	Temperature Compensated-Voltage Controlled Crystal Oscillator
TCXO	Temperature Controlled Crystal Oscillator
TD	Time Delay
TD	Transmitter Distributor
T-DAB	Terrestrial Digital Audio Broadcasting
TD-CDMA	Time Division Code Division Multiple Access
TDD	Telecommunications Device for the Deaf
TDD	Time Division Duplexing
TDF	Time Division Filtering
TDM	Time Division Multiplexing
TDMA	Time Division Multiple Access
TDMS	Time Division Multiplex System
TDMS	Transmission Distortion Measuring Set
TDOA	Time Difference of Arrival
TDR	Time Domain Reflectometer
TDRSS	Tracking and Relay Satellite System
TDS	Time Division Switching
TD-SCDMA	Time Division Synchronised CDMA
TE	Techno-Economic Evaluation
TE	Terminal Equipment
TE1	Terminal Equipment Type 1 (ISDN capable)
TE2	Terminal Equipment Type 2 (non-ISDN)
TE&DA	Techno-Economic Evaluation & Demand Analysis
TEAM	Techno-Economic Ad Hoc Meeting
TED	Trunk Encryption Device
TEDIS	Trade Electronic Data Interchange Systems
TEHO	Tail End Hop Off
TEI	Terminal Endpoint Identifier (LAPD)
TEK	Traffic Encryption Key
TELCO	Telecommunications Company
TELCOR	Instituto Nicaraguense de Telecomunicaciones y Correos (Nicaragua)
TELRIC	Total Element Long Run Incremental Costs
TEM	Transverse Electric And Magnetic
TEMA	Telecommunications Equipment Manufacturers Association
TeMIP	Telecommunications Management Information Platform (Compaq)
TEMPEST	Compromising Emanations
TEMS	Telecommunications Management System
TERENA	Trans-European Research and Education Networking Association
TeT	Techno-Economic Oriented Tools
TETRA	Trans European Trunked Radio
TFT	Thin-Film Transistor
TFTP	Trivial File Transfer Protocol
TFTS	Terrestrial Flight Telephone System
TG	Trunk Group
TGM	Trunk Group Multiplexer
THD	Total Harmonic Distortion
THF	Tremendously High Frequency
THL	Trans Hybrid Loss
THz	Terahertz
TI	Telecom Instruction
TIA	Telecommunications Industry Association (UK)
TIBS	Telecommunication Input Billing System (UK)
TIC	Token Ring Interface Coupler
TID	Terminal Identifier
TIE	Time Interval Error
TIFF	Tag Image File Format
TIG	Terminal Interoperability Group
TIM	Transmitter Intermodulation
TINA	Telecommunications Information Networking Architecture
TIOS	Transpath Input and Output Subsystem
TIP	Terminal Interface Processor
TIPHON	Telecommunications & Internet Protocol Harmonisation Over Networks
TIRKS	Trunk Information Record Keeping System (US)
TIS	Technical Information Sheets
TJF	Test Jack Frame
TK	Response Timer
TKK	Telekom-Control-Kommission (Austria)
TL	Transmission Level
TLH	Transport Layer Header
TLP	Transmission Level Point
TLP	Transmission Level Point
TLS	Transparent LAN Service
TLS	Transport Layer Security (IETF)
TM	Terminal Multiplexer
TM	Transmission and Multiplexing
TMA	Telecommunication Managers Association (UK)
TMF	Telecommunications Management Forum
TMN	Telecommunications Management Network
TMRS	Traffic Measurement and Recording Systems
TMS	Time-Multiplexed Switch
TMS	Transport Management System
TMSI	Temporary Mobile Subsciber Identity
TO	Tandem Office
TO	Telecommunications Operator
TO	Toll Office
TOA	Time of Arrival
TOC	Turn of Cycle
TOP	Technical Office Protocol
TOPS	Traffic Operator Position System
ToR	Terms of Reference
TOS	Temporarily Out of Service
ToS	Type of Service
TP	Toll Plant or Point
TP	Transaction Processing
TP	Transport Protocol (ISO)
TP	Twisted Pair
TPAU	Twisted Pair Attachment Unit
TPDU	Transport Protocol Data Unit
TPMR	Trunk Private Mobile Radio
TPON	Telephony over Passive Optical Network
TQM	Total Quality Management
TR	Token Ring
TR	Toll Restriction
TR	Transmit-Receive
TR VLAN	Token Ring Virtual LAN
TRA	Telecommunications Regulatory Authority (Bahrain)
TRA	Telecommunications Regulatory Authority (Oman)
TRA	Traffic Routing Administration
TRAI	Telecom Regulatory Authority of India
TRAC	Technical Recommendations Application Committee
TRANSEC	Transmission Security
TRAPI	Transport API
TRAU	Transcoder and Rate Adaption Unit
TRC	Telecommunications Regulatory Commission (Jordan)
TRC	Telecommunications Regulatory Commission of Sri Lanka
TRC	Transverse Redundancy Check
TRE	Telecommunications Regulatory Entity (Albania)
TRISL	Token Ring Inter-Switch Link
TRS	Telecommunications Relay Services
TRX	Transceiver
TS	Traffic Station
TS	Transmission Speed
TSAP	Transport Service Access Point
TSAPI	Telephony Services Applications Programming Interface
TSC	Transit Switching Centre
TSF	Telephone Service Factor
TSI	Time Slot Interchange
TSI	Transmitting Subscriber Information
TSK	Transmission Security Key
TSLRIC	Total Service Long Run Incremental Costs
TSM	Time Switch Module
TSP	Tag-Switched Path
TSP	Telecommunications Service Priority
TSPS	Traffic Service Position System
TSR	Telecommunications Service Request
TSR	Terminate and Stay Resident
TSRM	Telecommunication Standards Reference Manual
TSS	Tandem Switching System
TSS	Telecommunication Standardization Sector (ITU-T)
TSS	Telecommunications Terminal Equipment
TT	Dial Repeating Tie Line/Dial Repeating Tie Trunk
TT	Touch-Tone Adaptor
TT	Trunk Type
TTL	Transistor-Transistor Logic
TTL	Time-to-Live
TTP	Trail Termination Point (TMN)
TTPS	Trusted Third-Party Services
TTTEL	Trinidad and Tobago Telecommunications Authority
TRF	Tuned Radio Frequency
TTTN	Tandem Tie Trunk Network
TTY	TeleType
TTY	Telecommunications Device for the Deaf
TU	Tributary Unit
TUA	Telecommunications Users Association (UK)
TUD	Trunk Up-Down
TUG	Telecommunication User Group
TULIP	TCP and UDP over Lightweight IP
TUNIP	TCP and UDP over Nonexistent IP
TUR	Trunk Utilisation Report
TVR	Teletel Vitesse Rapide
TW	Travelling Wave
TWA	Two-Way Alternate (HDLC)
TWS	Two-way Simultaneous (HDLC)
TWT	Travelling Wave Tube
TWTA	Travelling Wave Tube Amplifier
TWX	Teletypewriter
TWX	Teletypewriter Exchange (Telex)
TX	Transmitter
TXD	Telephone Exchange Digital
TXE	Telephone Exchange Electronic
TXK	Telephone Exchange Crossbar
TXMTR	Transmitter
TXS	Telephone Exchange Strowger
U
U/L	Uplink
UA	Unbalanced Asynchronous (HDLC)
UA	Universal Access
UA	Unnumbered Acknowledgement (HDLC)
UA	User Agent
UAN	User Access Node
UART	Universal Asynchronous Receiver Transmitter
UAS	Unavailable Seconds
UAWG	Universal ADSL Working Group
UAX	Unit Automatic Exchange
UBR	Unspecified Bit Rate (ATM)
UC	Unified Communications
UCA	Utility Communications Architecture
UCC	Uganda Communications Commission
UCD	Uniform Call Distribution
UCM	Universal Call Model
UCP	Universal Computer Protocol
UCS	Universal Communications Standards
UCSP	Unified Communications Service Provider
UDI	Unrestricted Digital Information (ISDN)
UDLP	UniDirectional Link Protocol
UDP	User Datagram Protocol
UDP	User Datagram Protocol
UDSL	Unidirectional HDSL
UE	User Equipment
UHF	Ultra High Frequency
UI	Unnumbered Information (HDLC)
UISG	Utility Industry Standards Group
UITS	Unacknowledged Information Transfer Service (ITU-T)
UKAS	United Kingdom Accreditation Service
UKIUF	UK ISDN User Forum
UKPOA	UK Paging Operators’ Association
ULF	Ultra Low Frequency
ULL	Unbundling the Local Loop
ULP	Upper-Layer Protocol
UM	Unified Messaging
Um	GSM Air Interface
UMB	Upper Memory Block
UMS	Universal Messaging System
UMTS	Universal Mobile Telecommunications System
UN	Unbalanced Normal
UNI	User/Network Interface
UNITE	User Network for Information Exchange on Telecommunications in Europe
UNMA	Unified Network Management Architecture
UP	Unnumbered Poll
UPC	Usage Parameter Control (ATM)
UPCS	Universal Personal Communications Services
UPF	UnPlugFests
UPS	Uninterruptable Power Supply
UPT	Universal Personal Telecommunications
UPTAA	UPT Access Address
UPTAC	UPT Access Code
URL	Uniform Resource Locator
URM	Usage Reference Model
URSEC	Unidad Reguladora de Servicios de Comunicaciones (Uruguay)
URTiP	Office of Telecommunications and Post Regulation (Poland)
US	Universal Service
USART	Universal Synchronous Asynchronous Receiver Transmitter
USAT	Ultra Small Aperture Terminal
USB	Upper Sideband
USC	Universal Service Contribution
USIM	Universal Subscriber Identity Module
USIM	UMTS Subscriber Identity Module
USO	Universal Service Obligation
USOC	Universal Service Order Code
USP	Universal Service Provider
USSD	Unstructured Supplementary Service Data
USTA	United States Telephone Association
UT	Universal Time
UTC	Coordinated Universal Time
UTP	Unshielded Twisted Pair
UTRA	Universal Terrestrial Radio Access
UTRAN	Universal Terrestrial Radio Access Network
UUI	User-to-User Indentification
UUS	User to User Signalling
uv	Ultraviolet
UVM	Universal Voice Module
UVM-C	Universal Voice Module-Channelised
UVM-U	Universal Voice Module-Unchannelised
UWB	Ultra-Wideband
V
V/D	Voice/Data
V/FoIP	Voice and Fax over Internet Protocol
VA	Value-Added
VAD	Voice Activity Detection
VADS	Value Added Data Services
VADSL	Very High Speed ADSL (see VDSL)
VAN	Value-Added Network
VANS	Value Added Network Services
VAP	Value Added Process
VAR	Value-Added Reseller
VAS	Value Added Services
VB	Virtual Bandwidth
VBI	Vertical Blanking Intervals
VBNS	Very High Speed Backbone Network Service
VBR	Variable Bit Rate (ATM)
VBR-NRT	Variable Bit Rate-Non-Real-Time (ATM)
VBR-RT	Variable Bit Rate-Real-Time (ATM)
VC	Virtual Channel (ATM)
VC	Virtual Circuit (PSN)
VC	Virtual Container (SDH)
VCA	Voice Connecting Arrangement
VCC	Virtual Calling Card
VCC	Virtual Channel Connection (ATM)
VCD	Virtual Circuit Descriptor
VCI	Virtual Channel Identifier
VCI	Virtual Circuit Identifier (ATM)
VCL	Virtual Channel Link
VCS	Virtual Circuit Switch
VDSL	Very High-Speed Digital Subscriber Line
VDT	Visual Display Terminal
VDU	Visual Display Unit
VF	Variance Factor
VF	Voice Frequency
VFCT / VFCTG Voice Frequency Carrier Telegraph
VFDF	Voice Frequency Distribution Frame
VFO	Variable-Frequency Oscillator
VFTG	Voice-Frequency Telegraph
VG	Voice Grade
VGA	Video Graphics Adapter
VGF	Voice Grade Facility
VHDSL	Very High Bit Rate Digital Subscriber Line
VHE	Virtual Home Environment
VHF	Very High Frequency
VI	Vector Identifier
VIP	VINES Internet Protocol
VL	Vector Length
VLAN	Virtual LAN
VLBR	Very Low Bit Rate
VLF	Very Low Frequency
VLI	Virtual LAN Internetwork
VLSI	Very Large Scale Integration
VLSM	Variable-Length Subnet Mask
VM	Virtual Machine
VM	Virtual Memory
VMAC	Virtual Media Access Control
VMS	Voice Messaging System
VMSC	Voice Mail System Centre
VNL	Via Net Loss
VNLF	Via Net Loss Factor
VNS	Vehicle Navigation System
VNS	Virtual Network Service
VoATM	Voice Over ATM
vocoder	Voice-Coder
VoD	Video-on-Demand
vodas	Voice-Operated Device Anti-Sing
VoFR	Voice-over-Frame Relay
vogad	Voice-Operated Gain-Adjusting Device
VoHDLC	Voice over HDLC
VoIP	Voice over Internet Protocol
Volcas	Voice-Operated Loss Control And Echo/Signalling Suppression
Vox	Voice-Operated Relay Circuit
VP	Virtual Path
VPC	Virtual Path Connection
VPDN	Virtual Private Data Network
VPDN	Virtual Private Dial-up Network
VPI	Virtual Path Identifier
VPL	Virtual Path Link
VPLMN	Visited Public Land Mobile Netwok
VPN	Virtual Private Networks
VPT	Village Public Telephone
VQA	Voice Quality Assessment
VQT	Voice Quality Testing
VRC	Vertical Redundancy Check
VRML	Virtual Reality Markup Language
VRRP	Virtual Router Redundancy Protocol
VSA	Vector Signal Analyser
VSAM	Virtual Storage Access Method
VSAT	Very Small Aperture Terminal
VSB	Vestigial Sideband
VSI	Virtual Switch Interface
VSM	Vestigial Sideband Modulation
VSWR	Voltage Standing Wave Ratio
VT	Virtual Terminal (ISO)
VT	Virtual Tributary
VTAM	Virtual Telecommunications Access Method
VTE	Virtual Terminal Environment
VTOA	Voice and Telephony Over ATM
VTP	Virtual Terminal Protocol
VTU	Video Teleconferencing Unit
VU	Unit of Volume
W
W3C	World Wide Web Consortium
WAC	Wide Area Communication
WACS	Wireless Access Communications System
WADS	Wide Area Data Service
WAE	Wireless Application Environment
WAIS	Wide Area Information Services
WAN	Wide Area Network
WAP	Wireless Application Protcol
WARC	World Administration Radio Conference
WATS	Wide Area Telecommunications Service
WB/BB	Wide Band/Broadband
WBDTS	Wide Band Data Transmission Forum
WC	Wire Centre
WCDMA	Wideband CDMA
WCS	Wireless Communications Service
W-DCS	Wideband Digital Crossconnect System
WDM	Wavelength Division Multiplex
WDP	Wireless Datagram Protocol
WFQ	Weighted Fair Queuing
WG	Working Group
WGS	Worldwide Geodesic System
WiFi/WiMAX	Broadband wireless data technologies used for interconnecting computer equipment
WIN	Wireless In-Building Network
WIN	Wireless Intelligent Network
Winsock	Windows Socket API
WLAN	Wireless Local Area Network
WLL	Wireless Local Loop
WLS	Wireless Location Services (SignalSoft)
WM	Wireless Manager
WML	Wireless Markup Language
WP	Workpackage
WPBX	Wireless Private Branch Exchange
WPT	Wideband Packet Technology
WRC	World Radiocommunication Conference
WS	Workstation
WSF	Work Station Function Block
WSP	Wireless Session Protocol
WT	Wireless Transceiver
WTA	Wireless Telephony Application
WTLS	Wireless Transport Layer Security
WTO	World Trade Organisation
WTP	Wireless Transaction Protocol
wv	Working Voltage
WVDC	Working Voltage Direct Current
WWAN	Wireless Wide Area Network
WWDSA	Worldwide Digital System Architecture
WWW	World Wide Web
WWW3	World Wide Web Consortium
X, Y and Z
XA	Exchange Access (SMDS)
X-Bar	Crossbar Telephone Exchange
XC	Cross-Connect
xcvr	Receiver
XDF	Extended Distance Feature
xDSL	Generic Term for Digital Subscriber Line
xfmr	Transformer
XID	Exchange Identification (HDLC)
xistor, xstr	Transistor
XMIT	Transmit
XML	Extensible Markup Language
XMS	Extended Memory Specification
XMSN	Transmission
XMTD	Transmitted
XMTR	Transmitter
XNS	Xerox Network Systems
XOFF	Transmitter Off
XON	Transmitter On
XPD	Cross Polarisation Decoupling
XSM r	X Session Manage
XT	Crosstalk
XTagATM	Extended Tag ATM
Y2K	Year 2000
ZBTSI	Zero Byte Times Slot Interchange
ZCS	Zero Code Suppression
ZD	Zero Defects
ZIP	Zone Improvement Programme (US geographic codes)
ZIS	Zone Information Socket
ZIT	Zone Information Table
ZLE	Zero Latency Enterprise (Compaq)
ZNIIS	Central Research Telecommunication Institute - Russia
Zo	Characteristic Impedance
ZST	Zone Standard Time