PABX
Private Automatic Branch Exchange. Automated multi-extension exchanges or switchboards as used nowadays by most offices.

Peak
Highest-usage period of the business day when a cellular system carries the most calling traffic.

Pre-pay/Pay-as-you-go
Term used for no-contract, no rental charge services where you buy credit ‘vouchers’ in advance for calls. Each network has its own pre-pay service.

PBX
Private Branch Exchange. Multi-line switchboard exchange, as used in many offices.

PC card
Small accessory that allows you to connect a suitable digital mobile phone with a portable computer. Primarily designed for sending and receiving faxes and digital files (such as email).

PCMCIA card
An older term for the PC card.

PCN
Personal Communications Network. Another term for a GSM1800 network – such as Orange or One 2 One.

PCS1900
Personal Communications System operating in the 1900MHz band. Another name for GSM1900.

PDA
Personal Digital Assistant. A top-of-the-range personal organiser which allows you to store information and to use simple computer programs – as made by companies such as Psion. Also known as a palmtop computer. The Nokia 9110 Communicator is a PDA with a built-in mobile phone.

PMR
Private Mobile Radio. Type of mobile and walkie-talkie equipment commonly used by taxi firms, security guards, and utility companies. The advantage over cellphones is that once the equipment is paid for, and a licence is bought, there are no call costs.

Portable
A one-piece, self-contained cellular telephone. The newest portable model phones are so small - weighing as little as 3.1 ounces - that they can be folded up and carried in a suit pocket or purse. Portables normally have built-in antennas and a rechargeable battery. See also Mobile and Transportable.

PSTN
Public Switched Telephone Network. Technical term to describe the fixed, wired phone system – as operated by British Telecom.