The telecommunications industry delights in the use of acronyms, some of which are universally accepted, but many are specific to a particular corporation. Other acronyms may have more than one meaning, and can only be deciphered by the context.

            2B1Q     2 Binary 1 Quaternary

            4B3T     4 Binary 3 Ternary

           4WTS     4 Wire Terminating Set

              AAL     ATM Adaptation Layer

             ABM     Access Bandwidth Manager; Asynchronous Balance Mode [HDLC]

             ACD     Automatic Call Distributor

              ACF     Access Control Field [DQDB]

              ACK     ACKnowledgement

             ADM     Add Drop Multiplexer

         ADPCM     Adaptive Differential Pulse Code Modulation

               AIS     Alarm Indication Signal

              AMI     Automatic Mark Inversion

            AMPS     Advanced Mobile Phone Service

               ANI     Automatic Number Identification

              ANS     American National Standard

             ANSI     American National Standards Institute

            APPN     Advanced Peer to Peer Networking

              APS     Automatic Protection Switching

           ARDIS     Advanced Radio Data Information Service

              ARP     Address Resolution Protocol

      ARPANET     Advanced Research Projects NETwork

             ARQ     Automatic Repeat reQuest

            ASCII     American Standard Code for Information Interchange

             ATM     Asynchronous Transfer Mode

            AT&T     American Telephone & Telegraph

              AuC     Authentication Center [GSM]

               AUI     Attachment Unit Interface [Ethernet 802.3]


        BATMOS     Bipolar Analog Telecom Metal Oxide Semiconductor

        Bellcore     BELL COmmunications REsearch

             BCD     Binary Coded Decimal

              BCR     Bell Communications Research

              BER     Bit Error Ratio/Rate

            BHCA     Busy Hour Call Attempts

               BIP     Bit Interleaved Parity; Breaker Interface Panel

          B-ISDN     Broadband ISDN

            B-NT     Broadband Network Terminator

            BnZS     Binary n Zero Substitution [n = 3, 6, or 8]

             BOC     Bell Operating Company

             BOM     Beginning Of Message [DQDB]

      BORSCHT     Battery, Over voltage protection, Ringing, Supervision, Coding, Hybrid, Test

              bps     bits per second

              BRA     Basic Rate Access (2B+D, 144 Kbps)

               BRI     Basic Rate Interface [ISDN]

              BSC     Binary Synchronous Communications

                        Base Station Controller [GSM]

                BT     British Telecom

             B-TA     Broadband Terminal Adapter [ATM]

             B-Te     Broadband Terminal Equipment [ATM]

              BTS     Base Tranceiver Station [GSM]


      CAD/CAM     Computer Aided Design/Computer Aided Manufacturing

               CAI     Common Air Interface

              CAP     Competitive Access Provider

            CBDS     Connectionless Broadband Data Service

               CC     Central Control

             CCIR     Consultative Committee for International Radio

           CCITT     Comité Consultatif Internationale de Telegraphiqué et Telephoniqué

              CCS     Common Channel Signaling

              CCS     C [hundred] Call Seconds

               CD     collision detection; count down [DQDB]

           CDMA     Code Division Multiple Access

           CDPD     Cellular Digital Packet Data

              CDS     Copper Distribution Shelf

             CEC     Commission of European Communities

            CEPT     Conference on European Post & Telegraph

               CIR     Committed Information Rate [frame relay]

                CL     ConnectionLess

           CLASS     Custom Local Area Signaling Services

            CLNS     ConnectionLess Network Services [OSI]

            CLSF     ConnectionLess Server Function [ITU-T]

              CMI     Coded Mark Inversion

            CMIP     Common Management Interface Protocol [ISO]

             CMIS     Common Management Information Service [ISO]

             CMS     Call Management Services

               CO     Central Office

         CODEC     COder DECoder

             COM     Continuation Of Message

     COMPAND     COMpress exPAND

           CONS     Connection Oriented Network Service [ISO]

              CPE     Customer Premise Equipment

              CPY     Central Processor Unit

             CRC     Cyclic Redundancy Check

            CRTC     Canadian Radio and Television Commission

                CS     Convergence Sublayer

              CSC     Common Signaling Channel

            CSMA     Carrier Sense Multiple Access

      CSMA/CD     Carrier Sense Multiple Access with Collision Detection

              CT2     Cordless Telephone 2

              CT3     Cordless Telephone 3

             CTIA     Cellular Telephone Industry Association


               DA     Destination Address field

              DBS     Direct Broadcast Satellite

             DCM     Digital Carrier Module

              DCS     Digital Cellular System; Digital Channel Service; Digital Cross-connect System

             DCT     Digital Cordless Telephone

             DDD     Direct Distance Dialing

              DDS     Digital Data Service

             DEC     Digital Electronic Corporation

            DECT     Digital European Cordless Telecommunications

              DID     Direct Inward Dial

             DMS     Digital Multiplexing System

             DNA     Digital Network Architecture [Decnet]

           DNHR     Dynamic Non-Hierarchical Routing

             DOD     Direct Out Dial

               DP     Dial Pulse

             DPO     Dial Pulse Originating

              DPT     Dial Pulse Terminating

           DQDB     Distributed Queue Dual Bus [IEEE]

          DQPSK     Differential Quadrature Phase Shift Keying

             DS-0     Digital Signal type 0, 0 – 64 Kbps PCM channel

             DS-1     Digital Signal type 1, 24xDS-0 + 1 signaling bit (1.544 Mbps)

           DS-1c     DS-1 concatenated [2xDS-1]

             DS-3     Digital Signal type 3, 28xDS-1 (44.736 Mbps)

      DS-CDMA     Direct Sequence Code Division Multiple Access

            DSMA     Data Sense Multiple Access [Ardis]

              DSP     Digital Signal Processing

              DSU     Data Service Unit

              DSX     Digital cross-connect

            DTMF     Dual Tone Multiple Frequency

               DX     Digital eXchange

             DXC     Digital cross (X) Connect


              EBS     Electronic Business Set

             E&M     Ear and Mouth; a signaling method

            ECSA     Exchange Carriers Standards Association

               EIA     Electronics Industries Association

               EIR     Equipment Identity Register [GSM]

               EO     Electro-Optical

             EOM     End Of Message

          ERMES     European Radio MEssaging System

              ESF     Extended Super Frame

               ESI     External Synchronization Interface

              ESS     Electronic Switching System

             ESTI     European Telecommunications Standards Institute

              ETB     End of Transmission Block

             ETO     Equalized Termination Only

              ETR     Early Token Release

              ETX     End Of teXt


                  F     Flag

              FCC     Federal Communication Commission [US]

            FCOT     Fiber Central Office Terminal

              FCS     Frame Check Sequence

              FDD     Frequency Division Duplex

             FDDI     Fiber Distributed Data Interface (ANSI)

             FDM     Frequency Division Multiplexing

            FDMA     Frequency Division Multiple Access

              FDS     Fiber Distribution Shelf

              FEC     Forward Error Correction

              FEP     Front End Processor

               FM     Frequency Modulation

                FR     Frame Relay

              FSR     Frequency Selective Ringing

              FST     Fiber Services Terminal

              FT1     Fractional T-1

              FTP     File Transfer Protocol

                FX     Foreign eXchange

              FXO     Foreign eXchange Office

              FXS     Foreign eXchange Station [or services]


            Gbps     Giga bits per second

             GFC     Generic Flow Control

            GFSK     Gaussian filtered Frequency Shift Keying

           GMSK     Gaussian filtered Minimum Shift Keying

           GOSIP     Government Open System Interconnection Profile

             GSM     Groupe Speciale Mobile; Global System for Mobile communication


              HCS     Header Check Sequence [DQDB]

            HD3B     High-Density 3rd order Binary code

            HDLC     High-level Data Link Control [ISO]

            HDTV     High Definition TeleVision

             HEC     Header Error Control

      HIPERLAN     HIgh Performance European Radio LAN

              HLR     Home Location Register [GSM]

             HOB     Head Of Bus [DQDB]

             HRC     Hybrid Ring Control

            HSLN     High Speed Local Network


              IBM     International Business Machines Corp.

            ICMP     Internet Control Message Protocol

                ID     IDentification

            IDDD     International Direct Distance Dialing

             IDLC     Integrated Digital Loop Carrier

               IEC     Inter-Exchange Carrier

             IEEE     Institute of Electrical and Electronic Engineers

              IMEI     International Mobile Equipment Identity [GSM]

              IMSI     International Mobile Subscriber Identity [GSM]

             IMTS     Improved Mobile Telephone Service

             INMS     Integrated Network Management System

                 IP     Internet Protocol

             IPv6     Internet Protocol version 6

               IPX     Internetwork Packet eXchange protocol [Novell]

               IRL     Input Return Loss

             ISDN     Integrated Services Digital Network

      ISDN BRA     ISDN Basic Rate Access; otherwise known as 2B+D

      ISDN PRA     ISDN Primary Rate Access

          ISDN T     ISDN T interface

          ISDN U     ISDN U interface

             ISDU     Isochronous Service Data Unit [DQDB]

               ISO     International Standards Organization

              ISW     Inverted Synchronization Word

               ITU     International Telecommunications Union

               IVD     Integrated Voice Data

             IVDT     Integrated Voice Data Terminal

               IXC     Inter-eXchange Carrier


              JTC     Joint Techical Committee


              LAN     Local Area Network

           LAP-B     Link Access Procedure Balanced [X.25]

           LAP-D     Link Access Protocol D channel [ISDN]

              LAS     Local Analog Switch

            LATA     Local Access and Transport Area

             LCM     Line Card Module

            LCAP     Local Craft Access Panel

              LDS     Local Digital Switch

              LEC     Local Exchange Carrier

              LEO     Low Earth Orbit

             LGC     Line Group Controller

               LIC     Line Interface Controller

              LLC     Logical Link Control

              LSB     Least Significant Bit

              LSS     Locally Switched Services; services which terminate at the local office

                LT     Line Termination

              LTE     Line Terminating Equipment [SONET]


             MAC     Media Access Control

             MAN     Metropolitan Area Network

             MAU     Media Attachment Unit; Multistation Access Unit

             MBC     Meteor Burst Communications

              MBS     Meridian Business Services [or set]

              MCI     Microwave Communications Inc.

           MDMS     Mobile Data Base Station [CDPD]

             MDF     Main Distribution Frame

           MD-IS     Mobile Data Intermediate System [CDPD]

            M-ES     Mobile End System [CDPD]

             MIPS     Millions of Instructions Per Second

             MoU     Memorandum of Understanding

           MPEG     Motion Picture Encoding Group

               MS     Mobile Station [GSM]

           MTSO     Mobile Telecommunications Switching Office

             MTX     Mobile Telephone eXchange

             MUX     MUltipleXer


            NACK     Negative ACKnowledgment

          NAMPS     Narrow band AMPS

             NCP     Network Control Program

               NE     Networking Element

        NetBIOS     Network Basic Input/Output System protocol

              NFS     Network File Server

              NLS     Non-Locally Switched services; services which terminate and are switched at a remote office

               NM     Network Modules

             NMT     Nordic Mobile Telephone

              NNI     Network Node Interface

             NOS     Network Operating System

              NRZ     Non-Return to Zero

             NRZI     Non-Return to Zero with Inversion

              NSS     Non-Switched Services: use dedicated lines

               NT     Northern Telecom

          NorTel     Northern Telecom


             OAM     Operation Administration and Maintenance

         OAM&P     Operation, Administration, Maintenance, & Provisioning

            OC-1     Optical Carrier 1; an STS-1 signal optically encoded

            OC-3     Optical Carrier 3; an STS-3 signal optically encoded

             ONU     Optical Network Unit

             OPC     OPerations Controller

             OPX     Off Premises Extension

      OPX intra     an OPX served by a different CO

      OPX inter     an OPX served by the same CO

          OQPSK     Offset Quadrature Phase Shift Keying

               OS     Operating System

               OSI     Open Systems Interconnection


                PA     Pre-arbitrated Access [DQDB]

            PABX     Private Automatic Branch eXchange

            PACK     Positive ACKnowledgment

              PAD     Packet Assembler Disassembler [X.25]

              PBX     Private Branch eXchange

             PCN     Personal Communications Network

              PCS     Personal Communications System/Service

            PCSS     Personal Communications Satellite Services

             PDH     Plesiochronous Digital Hierarchy

             PDN     Public Data Networks

             PDU     Protocol Data Unit

              PHY     PHYsical layer

                PL     Pad Length

            PLCP     Physical Layer Convergence Procedure [DQDB]

               PM     Peripheral Module; Performance Monitoring; Physical Medium

             PMD     Physical layer Medium Dependent

             POH     Path OverHead [SONET]

             PON     Passive Optical Network

             POP     Point of Presence

              POS     Point Of Sale

            POTS     Plain Ordinary Telephone Service

              PPP     Point to Point Protocol

            PPSN     Public Packet Switched Network

              PRA     PRimary Access rate i.e. 23B+D or 30B+D

               PRI     Primary Rate Interface [ISDN]

            PSDS     Public Switched Digital Service

            PSTN     Public Switched Telephone Network

            PTAT     Private Trans Atlantic Telecommunications

              PTT     Post, Telegraph and Telephone

              PVC     Permanent Virtual Circuit


               QA     Queued Arbitrated access; Quality Assurance

           QCPM     Quadrature Continuous Phaseshift Modulation

              QoS     Quality of Service

            QPSK     Quadrature Phase Shift Keying

            QPSX     Queued Packet and Synchronous eXchange


            RACE     Research and development in Advanced Communications for Europe

           RBOC     Regional Bell Operating Company

            RDPS     Reverse Direction Protection System

              RFT     Remote Fiber Terminal

             RISC     Reduced Instruction Set Computer

               RQ     ReQuest

                RZ     Return to Zero


              SAA     Service Adaptive Access

              SAP     Service Access Point

              SAR     Segmentation And Reassembly

              SCP     Service Control Points

              SDH     Synchronous Digital Hierarchy

            SDLC     Synchronous Data Link Control [IBM]

              SDU     Service Data Unit

          S/DMS     SONET Digital Multiplexing System

                SF     Super Frame

               SIM     Subscriber Identity Module [GSM]

               SIP     Smds Interface Protocol

             SLIC     Subscriber Line Interface Circuit

            SMDS     Switched Multi-megabit Data Service

              SMS     Short Message Service [GSM]

            SMTP     Simple Mail Transfer Protocol

              SNA     Systems Network Architecture [IBM]

               SNI     Subscriber Network Interface [SMDS]

            SNMP     Systems Network Management Protocol

             SOH     Section OverHead

          SONET     Synchronous Optical NETwork

          SPADE     Single channel, Pulse code modulation, multiple Access, Demand assignment Equipment

              SPE     Synchronous Payload Envelope [SONET]

         SPRING     Shared Protection RING

              SSB     Single Side Band

            SSDN     Special Services Digital Network

              STM     Synchronous Transfer Mode

           STM-1     Synchronous Transport Mode level 1 [3xSTS-1, STS-3c]

              STP     Shielded Twisted Pair; Spanning Tree Protocol

              STS     Synchronous Transport Signal

           STS-1     Synchronous Transport Signal level 1 [51.84 Mbps]

           STS-3     Synchronous Transport Signal level 3 [155.52 Mbps]

          STS-3c     Concatenated STS-3

              SVC     Switched Virtual Circuit; Signaling Virtual Channel

               SW     Synchronization Word

              SYN     SYNchronous idle


                TA     Terminal Adapter

            TACS     Total Access Communications System

             TADI     Time Assignment Data Interpolation

             TASI     Time Assignment Speech Interpolation

             TBM     Transport Bandwidth Manager

             TCM     Time Compression Multiplexing

         TCP/IP     Transmission Control Protocol/Internet Protocol

             TDD     Time Division Duplex

             TDM     Time Division Multiplexing

           TDMA     Time Division Multiple Access

                TE     Terminal Equipment

           Telco     Telephone company

              THL     Trans-Hybrid Loss

               TIA     Telecommunications Industry Association

                TP     Twisted Pair; Tip Party

                TR     Technical Report

               TSI     Time Slot Interchange

              TSS     Transport Services Shelf; a component of DMS AccessNode


            UDLC     Universal Digital Loop Carrier

             UDP     User Data Protocol [internet]

            UMTS     Universal Mobile Telecommunications Service

              UNI     User Network Interface

              UTP     UnTwisted Pair


              VAN     Value Added Network

              VBR     Variable Bit Rate

               VC     Virtual Channel [ATM]; Virtual Call [X.25]

               VCI     Virtual Channel Identifier

                VF     Voice Frequency

              VLR     Visitor Location Register [GSM]

             VLSI     Very Large Scale Integration

                VP     Virtual Path

               VPI     Virtual Path Identifier

            VSAT     Very Small Aperture Terminal

                VT     Virtual Tributary (SONET)

           VT1.5     VT ~1.5 Mbps [capable of carrying a DS-1]


            WAN     Wide Area Network

           WARC     World Administrative Radio Conference

           WATS     Wide Area Telecommunication Service

            WBC     Wide Band Channels

            WDM     Wave Division Multiplexing


                 XI     X.25 SNA Interconnect


           ZBTSI     Zero Byte Time Slot Interchange