BT glossary - P

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.

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Abbreviation Term Definition



A data transmission unit of data containing user information and header information such as the source and destination addresses, packet length and the protocol type. Sent from one computer to another, usually via a network.


Packet switching

The method used to move data around on the internet. In packet switching, all the data coming out of a machine is broken up into chunks, each chunk has the address of where it came from and where it is going. This enables chunks of data from many different sources to co-mingle on the same lines, and be sorted and directed to different routes by special machines along the way. This way many people can use the same lines at the same time.



A radio system for alerting users, causing a body-worn device to 'bleep' or vibrate. Tone-only pagers do just this, whereas message pagers can display a telephone number or an alphanumeric message. A few voice-paging systems also pass an audible message. Generally paging systems are one-way only but a few allow the person receiving the message to press a button to send a signal indicating acknowledgement. Local systems generally cover a single user's site (e.g. a hospital or a factory), whereas wide-area networks cover all or most of a country. Also called radiopaging.


Parental Control

Parental Control enables you to decide which websites your children can and can’t see, protecting them from porn or sites with a violent or offensive content.


Peer-to-peer networking

A network that enables any site to communicate directly with any other site.



Peripheral Component Interconnect

A bus (interface) standard for adapter cards in PCs, designed by Intel. It provides a direct, 32-bit wide data path from the peripheral to the PC's CPU and main memory.



Personal Communications Network

A digital cellular radio service for pocket telephones operating at a frequency around 1800MHz (1.8GHz). PCN is seen very much as the next generation of cellular radio and could additionally, in some markets, become the standard means of providing residential telephone service.



Personal Communications Service

The American name for PCN. There is not much difference in meaning now, though originally it was thought that PCN and PCS might evolve in different directions.



Personal Computer Memory Card International Association

An industry association. The term is also used as shorthand for the standard it has devised for plug-in devices to be connected to notebook PCs. These can include modems, network cards and hard disks. PCMCIA devices are now known as PC-Cards.



Personal Digital Assistant

A handheld computer device, typically offering access to diary information, contact lists and other information synchronised to a desktop computer. Can also act as a mobile communication device.


Personal number

A true personal telephone number relates to an individual, not to a fixed physical location, and should not be tied to a specific network provider or type of service. It could, at least in theory, be a number for life. See also Portable Number.



Phising are emails pretending to be from a known and trusted company, like your bank, phone company or ebay, where they ask you to re-submit your personal details, password or even account number. They can be hard to distinguish from genuine emails as the look and design will look like official communications. This is a tool for fraud and identity theft.



Plain Old Telephone Service



Pop-up blocker

Pop-ups are small windows that open when you are on a website. They often contain advertisements, surveys or links to other internet sites. The pop-up blocker stops them from appearing and obstructing your view.



A Portal is a website or service that offers a broad array of resources and services, such as email, forums, search engines and online shopping malls. The first web portals were online services, such as AOL, that provided access to the web, but by now most of the traditional search engines have transformed themselves into web portals to attract and keep a larger audience.



Post Office Protocol

Post Office Protocol. POP collects email messages addressed to you and downloads them to your computer when you check your email. You cannot store your messages on a POP email server. Make a note of your POP (incoming mail) server in case of problems with email.



Point to Point Protocol

Most well known as a protocol that allows a computer to use a regular telephone line and a modem to make TCP/IP connections and thus be really and truly on the Internet.


Portable number

A telephone number that is part of a national numbering scheme but is not tied to a particular network operator. Subscribers changing service provider would be able to take their portable number with them and thus not have to change number when they changed network. See also Personal Number.



Usually used as a marketing term to describe a web site that is or is intended to be the first place people visit when using the web. Typically a portal site is a catalogue of web sites, a search engine, or both. A portal site may also offer email and other services to entice people to use that site as their main point entry (hence portal) to the web. An example is BTopenworld.



Post Office Protocol

Refers to the way e-mail software such as Eudora gets mail from a mail server. When you obtain a SLIP, PPP, or shell account you almost always get a POP account with it, and it is this POP account that you tell your e-mail software to use to get your mail.


Predictive dialler

A mechanism for dialling calls automatically and handing them to agents for completion once the called number has answered. The dialler makes more calls than there are agents available, on the predicted basis that not all calls will mature and some will either fail in the network or go unanswered. The ratio of called dialled to agents available will vary according to the time of day and week and is held within the software. In the rare event of more calls maturing than there are unoccupied agents, an apology message is played out to the called party. The term power dialler is another name for the same technique.



Private Automatic Branch Exchange

A telephony switch that allows users to make calls to other telephones on the same site and into the public network without intervention of an operator.


Private automatic exchange

Used in the USA as a synonym for PABX. In Britain used to designate a private telephone system which allows automatic connection between telephone users (i.e. unassisted by a switchboard operator) on site or within the private network but with no connection whatsoever to the public network. Decidedly uncommon since the mid-1970s but once commonplace.


Private circuit

A point to point connection providing a fixed amount of allocated bandwidth.


Private key

A key used in asymmetric encryption and kept secret by a principal. It can be used to encrypt messages to provide authentication and non-repudiation, and to decrypt messages signed with the corresponding public key to provide confidentiality.



Private Mobile Radio

A generic term for what many people would describe more simply as business radio. Taxi despatch systems are probably the most common example with which people are familiar. User equipment can be mobile phones in vehicles or handheld walkie-talkies.


Private network

A network of inter-switchboard circuits on leased lines and/or VPN facilities connecting an organisation's different locations and used for the organisation's own business to avoid having to make public network calls.


Private wire

The name nearly everyone still gives to Private Circuits (point-to-point lines provided for a subscriber's exclusive use). Colloquially known as Hotlines.


Public key

A key used in asymmetric encryption that is made public to other principals in the system, often by the use of a certificate issued by a certification authority. Can be used to decrypt messages signed by the user's private key, or to sign messages so that only the owner of the private key can decrypt them.



Public Network Operator

A business that sells telecommunication services to the public. An alternative expression for PTO.



Public Switched Telephone Network

The Public Switched Telephone Network is the proper name for BT's UK phone network.



Public Telecommunications Operator

A business offering PSTN and other communication services.


Permanent Virtual Circuit

A pre-established virtual circuit. see Virtual Circuit and Frame Relay.