This is a list of telephony terminology and acronyms which relate to telephony networks.

A

  • Advanced Intelligent Network, (AIN), see also IN or Intelligent Network
  • Automatic number announcement circuit (ANAC)
  • Automated Attendant
  • ACD - Automatic Call Distribution
  • Articulation score

B

  • Blue box - a device that was used to bypass the normal long-distance call switching tones typically used to obtain free calls.

C

  • Call originator - (or calling party, caller or A-party) a person or device that initiates a telephone call by dialling a telephone number.
  • Call waiting - a system that notifies a caller of another incoming telephone call by sounding a sound in the earpiece.
  • Called party - (or callee or B-party)
  • Caller
  • Calling party
  • Conference call (multi-party call)
  • COCOT
  • Cutunexpected, and usually sudden, termination of call, line or service

D

  • Dial peer
  • Dial tone
  • Distribution frame
  • Dual-tone multi-frequency signaling (DTMF)

E

  • Emergency telephone number
  • End instrument
  • Engset calculation
  • Erlang unit

F

  • Fax - (contraction of facsimile) a device connected to the telephone network to enable documents to be scanned and sent to a receiving fax machine
  • Frame - A distribution frame, a set of open wiring racks where circuits are cross connected to trunks and equipment

H

  • Handoff
  • Handover
  • Help desk
  • Howler tone (see ROH tone)
  • Hunt Group

I

  • Infrastructure
  • Intelligent Network (IN)
  • Interface functionality
  • Inside plant
  • Intelligent Network Interface Device (iNID) - replaces the Network Interface Device outside a subscriber's house like when customers subscribe to AT&T's U-verse brand of services.
  • Interactive voice response (IVR)
  • ISDN User Part (ISUP)

L

  • Line
  • Local loop
  • Long-distance operator

O

  • On-premises wiring
  • Operator assistance
  • Outside plant

P

  • PAM - Pulse Amplitude Modulation used to convert an analog signal to digital representation of the analog signal in each channel of a "D" Type carrier system
  • PCM - Pulse Code Modulation is a modulation scheme used to transmit digital binary data in a T1 system
  • Permanent signal
  • Person-to-person
  • Plain old telephone service, or "POTS"
  • Public Switched Telephone Network (PSTN)
  • Pupinization

R

  • Receiver Off-Hook tone (ROH)
  • Red telephone box
  • Red box
  • Regional Bell Operating Company (RBOC)
  • Ringer equivalency number (REN)
  • Ringing signal
  • Rural radio service

S

  • Smartphone
  • Station-to-station
  • Signalling System 7 (SS7)

T

  • Tandem signaling
  • Tandem switch
  • Transaction Capabilities Application Part (TCAP)
  • Telemarketing
  • Telephone
  • Telephone booth
  • Telephone call
  • Telephone card
  • Telephone directory
  • Telephone exchange
  • Telephone tapping
  • Teletraffic engineering
  • T1 - Digital PCM (pulse code modulated signal) transmission system based on 1's and 0's and a speed of 1.544mbps
  • Time Division Multiplexing (TDM)
  • Toll-free_telephone_number (TFN) A telephone number that is billed for all arriving calls, but free for the calling party.
  • Trap and trace
  • TWX

U

  • USOC Universal Service Order Code

V

  • Vertical service code
  • Voicemail
  • Voice over Internet Protocol (VoIP)

W

  • Western Union
  • Wide Area Telephone Service (WATS)
  • WATS line
  • Wireless network
  • Wireless Telephony Applications Interface (WTAI)
  • Wi-Fi

Z

  • Zenith number

Acronyms

{| border=1 style="border-collapse:collapse" cellspacing=0 cellpadding=5

! Acronym

! Name

! Notes

|-

| 1ESS || Number 1 Electronic Switching System (Alcatel-Lucent) || US

|-

| 1FR || Flat rate service || US

|-

| 2G|| second-generation mobile telephone ||  

|-

| 2.5G|| Enhanced 2G mobile telephone ||  

|-

| 3G|| third-generation mobile telephone ||  

|-

|4ESS

|Number 4 Electronic Switching System (Alcatel-Lucent)

|

|-

| 4WTS || Four-wire termination set || US

|-

|5ESS

|Number 5 Electronic Switching System (Alcatel-Lucent)

|

|-

| ACD|| Automatic Call Distribution/Director || 

|-

| ACTS || Advanced Coin Telephone Service || US

|-

| ADSL || Asymmetric Digital Subscriber Line ||  

|-

| ANI || Automatic Number Identification || US

|-

| AMA || Automatic Message Accounting || US

|-

| BOK || Unblocking || UK

|-

| CCIS || Common Channel Interoffice Signaling ||  

|-

| CID || Caller ID ||  

|-

| CLEC || Competitive Local Exchange Carrier || US

|-

| CLI || Caller Line Identification || Europe

|-

| CLID || Caller Line ID || UK

|-

| CTI || Computer telephony integration || 

|-

| COSMOS || Wire records || 

|-

| DDCO|| Direct Dial Central Office (Opposite of DID) || US

|-

| DDD|| Direct Distance Dialing || US

|-

| DDI || Direct Dialing In || UK

|-

| DECT || Digital Enhanced Cordless Telecommunications ||  

|-

| DID || Direct Inward Dialing || US

|-

| DMS || Digital Multiplex System (e.g. DMS-100) || Can

|-

| DNIS|| Dialed Number Identification System || US

|-

| DSL || Digital subscriber line ||  

|-

| DTMF || dual-tone multi-frequency ||  

|-

| FDM || Frequency-division multiplexing ||  

|-

| GPRS || General Packet Radio Service ||  

|-

| GSM || Global system for mobile communications ||  

|-

| GST || Ground Start Trunk || US

|-

| IDDD || International Direct Distance Dialing || US

|-

| IDF || Intermediate distribution frame || US

|-

| ILEC || Incumbent Local Exchange Carrier || US

|-

| ISD || International Subscriber Dialing || UK and India

|-

| ISDN || Integrated Services Digital Network ||  

|-

| IVR || Interactive Voice Response (a.k.a. VRU) ||  

|-

| KSU || Key Switching/System Unit || US

|-

| LST || Loop Start Trunk || US

|-

| MDF || Main Distribution Frame ||  

|-

| MF || Multi-frequency || US

|-

| PABX || Private Automatic Branch eXchange || Europe

|-

| PBX || Private Branch eXchange || US

|-

| PMBX || Private Manual Branch eXchange || UK

|-

| POTS || Plain Old Telephone Service ||  

|-

| PSTN || Public Switched Telephone Network ||  

|-

| RCMAC || Recent Change Memory Administration Center || US

|-

| REN || ringer equivalency number ||  

|-

| SMS || Short Message Service (i.e. text messages) ||  

|-

| SF || Single Frequency supervision tone (2600) || US

|-

| SIP || Session Initiation Protocol || US

|-

| SP Lock || Unlocking|| UK

|-

| SS7 || Signaling System 7 ||  

|-

| STD || Subscriber trunk dialling || UK and India

|-

| T-CXR || T-carrier (e.g. T-1) || US

|-

| TAPI || Telephony Application Programming Interface ||  

|-

| TFN || Toll-free telephone number ||  

|-

| TR || Tip and ring || US

|-

| TSPS || Traffic Service Position System ||  

|-

| TXE || Telephone eXchange Electronic || UK

|-

| UAX || Unit Automatic eXchange || UK

|-

| VoIP || Voice over Internet Protocol || US

|-

| WAP || Wireless Application Protocol ||  

|-

| WATS || Wide Area Telephone Service || US

|-

| WTAI || Wireless Telephony Applications Interface ||  

|}