Telecommunication definitions and glossary

Simple definitions of common terms used in telecommunications, PBXs and call accounting.


Abandoned call

A call that has been terminated before being answered or while on hold.

Account code

A code entered into a telephone handset before, during or after a call. The code is associated with the call in CDR or SMDR data and can indicate information such as the customer or call type.


Automatic Call Distribution. The ACD manages telephone queues, so that the call that has been waiting the longest is answered first. Certain inbound numbers can be given higher priority.


Automatic Number Identification. Allows the receiver of a telephone call to display and record the phone number that originated the phone call.

Auto Attendant

A virtual receptionist than allows calls to be automatically transferred to an extension without human intervention. Typically performed by the use of a simple menu, for example, press 1 for sales, press 2 for support.


Busy Tone. The sound made by a PBX handset when the called party is busy.

Call accounting

Call accounting is an application that collects metadata about telephone usage and assigns call costs for later reporting. It may also be known as 'call analytics', 'call logging' or 'call reporting'.

Caller ID

Displays the calling party's number or name before the call is answered.


Call Detail Record. This is the information that a PBX, key system or other telephone exchange equipment makes available to a connected device, typically a computer. This information describes each telephone call as it happens and includes information such as the call time and duration.


Central Office. A call that is generated by a PBX such as when an extension is on permanent diversion. The call will often show in reports as the extension 'CO'.

CSV, .csv

Comma Separated Values. A file with fields of each record separated, or delimited, by commas. Each record is separated from the next by a carriage return and new line characters, for example \r\n. A .csv file can be loaded into Microsoft Excel.


Direct Inward Dialing (DID) also known as Direct Dialing In - a way of directly dialing a person, or a hunt/ring group, even though they are an extension on large PBX. A DDI phone number is the number that was dialed by a person dialing in to your PBX.


Dialed Number Identification Service. DNIS indicates the number that was orginally dialed which may be different than the resulting end phone number due to call forwarding.


A PBX typically has a number of telephone handsets. In addition to the handsets a PBX might have many extensions that are not visible to the user such as hunt groups, queues and other virtual extensions. These extensions are not usually seen by the user but are used internally by the PBX.

External call

External calls are those calls made between a telephone outside your business and a telephone inside your business and use a trunk.


A station is the telephone extension, for example extension 100 or extension 101. See Station.

Hunt group

A group of telephone extensions tied to a telephone number.

Incoming call

Incoming calls are those calls that are made into your PBX from the public telephone network.

Internal call

Internal calls are those calls made from one extension to another.


Integrated Services Digital Network. ISDN is set of standards for simultaneous transmission of data, video, voice and other services over the standard telephone network.


Interactive voice response. A technology that enables people to interact with a computer over a telephone by pressing numbers on the phone keypad or by voice commands.


Key Telephone System. KTSes are small business telephone systems that generally are used where the requirement is for 2 to 100 stations, and where there is a large number of internal intercom calls in relation to the number of inbound or outbound calls.


See Trunk.


Metadata is a set of information that describes other data. For example, when a telephone call occurs the metadata generated describes the number dialled, how long it took the call to be answered and the duration of the call.

Multipart call

Calls that involve more than one extension (for example a call that is transferred from one extension to another) are called multipart calls.

Outgoing call

Outgoing calls are those calls made from an extension on your PBX out to the public telephone network.


Private Automated Branch Exchange / Private Branch Exchange. This is the multiple telephone handset equipment (usually) installed at your premises.


PDR is the in-house term for user support requests, it is an abbreviation of 'Product Defect Report'. Users can submit a support request via the 'Help & support' page.


Plain Old Telephone Service. This is the traditional, wired, world-wide telephone system.


Public Switched Telephone Network. This is the traditional, wired, world-wide telephone system.


Quality of Service. Refers to the overall quality of the telephone service and deals with things like the clarity of the call, delays in speech and other errors in the call.

Ring out

An call was not answered for so long the PBX or telephone company gave up and terminated the call.

Ring time

The ring time is the duration the telephone rang before being answered.


Station Management Detail Recording. This is the information that a PBX makes available to a connected device, typically a computer. This information describes each telephone call as it happens and includes information such as the call time and duration.


A station is the telephone extension, for example extension 100 or extension 101.


Subscriber trunk dialing (STD, also known as subscriber toll dialing) is a telephone system allowing subscribers to dial trunk calls without operator assistance.

Station group

A hunt group used during a period of time, for example, during a marketing campaign.

Tandem call

A call between two outside lines. The two outside lines may have been joined by a user on an extension who may then drop out of the call. Alternatively an inbound call may have automatically forwarded to another outside line.


A trunk is the telephone line provided by your telephone company. A residential address typically has a single telephone line. An office typically has more than one line.

Trunk group

A trunk group is a number of similiar trunks, for example lines from a single telephone company or a number of trunks with the same cost.

Two-step authentication

Two-step authentication (2FA) requires two different types of authentication such as 1 what you are (finger print or iris scan), 2 what you know (password or secret phrase) or 3 what you carry (identification or swipe card).

Two-step verification

Two-step verification can use the same type of identification from two different providers, for example a password and a one-time code from a security token or authenticator app.

TXT, .txt

Text file. A file with records separated, or delimited, by tabs. A .txt file is a very simple file format that can be read on virtually any computer.


Universal Time, Coordinated. Shares the same time as GMT (Greenwich Mean Time). World times are offset from this standard time.


Voice over Internet Protocol. A means of using the internet to make telephone calls. Depending on the installation and service used there may be very little to distinguish a VoIP telephone call from a PSTN call including quality of service and the physical appearance of telephone handsets.

XML, .xml

eXtensible Markup Language. A general-purpose specification used to create custom definitions describing how data is structured. Widely used to share information over the internet between computers, regardless of operating system.