ADSL (Asynchronous Digital Subscriber Line) 

Asynchronous Digital Subscriber Line, allows a standard telephone line to be used like a broadband line for transmission of large amounts of data.

CLI (Calling Line Identification)

Calling Line Identification or Caller ID, allows inbound call number to be identified before answering (systems).

CPS (Carrier Pre-Selection)

The selection of alternative communications providers to carry their calls without having to dial a prefix, or install any special equipment at their premises. .

DECT (Digital Enhanced Cordless Technology)

Digital Enhanced Cordless Technology, a global standard for digital wireless telephones (but not mobiles).

DDI (Direct Dial In)

Direct Dial In, allows external calls to go directly to an extension without being transferred via a switchboard.

Fibre To The Cabinet (FTTC)

This is a generic term for any broadband service that uses fibre optic cable, in place of traditional copper wiring, to connect a telephone exchange to the ‘green cabinets’ in the surrounding roads.

Hunt Group

Multiple phones allocated to a single DDI or extension number, thereby enabling an inbound call to be answered from any phone, within the allocated group of phones.  Inbound calls can be configured to ‘hunt’ from one phone to another (until answered) or to be “broadcast” across all phones in the group, so they all ring at once.

IP (Internet Protocol) telephony

Internet Protocol Telephony, standard governing transmission of data and calls via the Internet.

ISDN (Integrated Services Digital Networks)

Integrated Services Digital Networks allow digital transmission of data via traditional copper wires. ISDN offers greater capacity and faster transmission than analogue.


Provided in pairs i.e. 2 channels/lines per ISDN2e. The majority of customers would get a maximum of 4 pairs before moving up to ISDN30e. The e stands for the European standard


Provided over one large circuit (bearer/pipe) either as copper or in many cases fibre optic.  The minimum number of channels/lines one can have is 8 moving up to 30.  Larger organisations can rent multiple ISDN30’s should they require more lines.  The e stands for the European standard.

IVR (Interactive Voice Response)

Interactive Voice Response, technology which defects voice and touch tone signals to initiate call direction eg For Accounts, press 1.

LCC (Least Cost Call)

Least Cost Call, service provided by telecom carriers minimising call costs through selection of lowest cost routes.

LCR (Least Cost Routing)

Least Cost Routing, a service provided by telecom carriers to reduce call spends on outbound calls.

LLU (Local-loop Unbundling)

Local-loop Unbundling; is the process of allowing multiple telecommunications operators to use connections from the telephone exchange.


Stands for ‘Multi Protocol Label Switching’ – A flexible and cost effective way of providing a WAN.

NGN (Non-Geographic Number)

Non-Geographic Number, the term refers to the 08/03 non-geographic number including UK 0800 numbers and free 0844 numbers rather than the 01/02 geographic number.

PBX (Private Branch Exchange)

Private Branch Exchange, an exchange serving a particular organisation, connecting internal phones and externally to the Public Switched Telephone Network (PSTN).

PSTN (Public Switched Telephone Network)

Public Switched Telephone Network which comprises the world’s public telephone systems. Also referred to as the Plain Old Telephone System (POTS) it provides the Internet’s infrastructure.

QOS (Quality of Service)

Quality of Service, to provide a service level guarantee on a business network.


A device (or, in some cases, software on a computer) that directs IP packets to the next point toward their destination.

SDSL (Symetric Digital Subscriber Line)

The same as ASDL but provides the same speed/bandwidth in both directions. Ideal for companies needing to upload high bandwith packets quicker than ADSL. A common requirement with VOIP networks.

SIP (Session Initiation Protocol)

Session Initiation Protocol, enables calls to be routed via the internet rather than a telephone network.

SIP Trunks

Basically an internet phone line.  Part of the broadband bandwidth is allocated solely for a VoIP call.  Each VoIP call requires one SIP trunk but a good quality broadband service can accommodate multiple SIP trunks.


Stands for ‘Service Level Agreement’ – part of a service contract where the level of service is formally defined. In practice, the term SLA is sometimes used to refer to the contracted delivery time (of the service) or performance.

VoIP (Voice Over Internet Protocol)

Voice Over Internet Protocol, standard governing voice transmission via the Internet.

Unified Messaging

Enables you to access voice, fax, and text messages via one single email or telephone account.


Stands for ‘Virtual Private Network’ – A way of creating a private communications network over a public network (mostly the internet) using secure protocols (passwords, authentication methods etc).