BT glossary - F

This glossary is here to help you understand some of the acronyms you may encounter in this site. Select a letter below that your word begins with.

A    B    C    D    E    F    G    H    I    J    K    L    M    N    O    P    Q    R    S    T    U    V    W    X    
Abbreviation Term Definition


Fibre Distributed Data Interface

A 100 Mbit/s USA standard for optical fibre voice + data cabling in buildings. It features a dual ring, offering protection from a device or link failure.


File Transfer Protocol

This is a method for transferring publicly accessible documents between machines or over the Internet.



A security device that stops others having uninvited access to your computer. Hardware firewalls are built into devices such as routers. Software firewalls are special computer programs loaded onto your devices. Your service provider will advise you on appropriate security measures.


Flexible Bandwidth Service

Offers a more manageable, resilient and flexible way of providing multiplexed bandwidth.



A packet of data including start and end of frame delimiters.


Frame relay

Connection oriented WAN (Wide Area Network) which caters for bursty traffic.


Frequency Division Multiplex

A transmission system in which different channels are assigned to individual frequencies.


Frequency Modulation

A process by which, say, music is transmitted using a radio signal. Input audio-frequency signals modify the frequency of the transmitted signal around its nominal value.


BT Fusion

The world's first combined fixed and mobile phone service. BT Fusion works just like a mobile phone when you are out and about, but switches automatically and seamlessly onto a BT Broadband line when you get home.