Glossary

ISDN

Integrated Services Digital Network – A type of subscriber line that connects customer equipment to the outside world. These can be used for voice or data, but typically used for voice traffic when connected to a private branch exchange (ie office telephone system). An ISDN circuit can be delivered over copper wires or fibre cable and consists of 32 channels, of which 30 are useable. ISDN offers much higher functionality than analogue lines.

PSTN

Public Switched Telephone Network – A generic term given to the network of telephone exchanges around the world that interconnect, allowing users to dial each other. In some cases this will also refer specifically to analogue or digital subscriber lines, such as ISDN.

ADSL

Asymmetric Digital Subscriber Line – Otherwise known as “Broadband”. There are many different variations and modes that can help increase speeds or reliability. ADSL is almost always delivered entirely over the traditional copper connection from the local telephone exchange. Asymmetric means it has higher bandwidth downstream than upstream.

 
FTTC

Fibre to the Cabinet – An asymmetric internet connection delivered partially by a fibre optic cable. The fibre usually terminates in the local distribution cabinet (those green boxes in the street), with the last part of the connection delivered over the usual copper telephone cabling. These provide higher speeds due to the significantly shorter distance over copper.

FTTP

Fibre to the Premises – An asymmetric internet connection delivered using a fibre optic cable straight into your property. These can deliver very high speeds and are very reliable.

VoIP

Voice over Internet Protocol – The general term given to transmitting a voice call over the internet. There are many forms of VoIP, with the main two being H.323 and the more prevalent SIP. 

SIP 

Session Initiation Protocol – Where VoIP is a generalised term for sending voice over a data network, SIP is a specific form of that. It’s describes a set of rules which all devices that support SIP must adhere to, so that lots of different devices can operate together.

PBX (or PABX)

Private Branch Exchange – What people normally know as their office phone system. It’s a telephone system that handles internal calls between users, as well as aggregating a set amount of connections to the outside world (PSTN). These phone systems are usually feature rich, providing functionality that you don’t normally get on a residential line such as group pick-up, call parking, call distribution and much more. These systems can vary in size and complexity from a handful of extensions up to many thousands of extensions across multiple sites and locations.

DECT

Digital Enhanced Cordless Telecommunications – Or, “walkabout phone”. DECT describes a set of rules and frequencies that all cordless telephones need to adhere to. It provides interoperability between manufacturers of handsets, base stations and phone systems. It also allows the user to roam between networked base stations without dropping a call, so you can maintain connection as you walk throughout your premises.