An index of all the common telecoms terms, jargon and acronyms.

Telecommunications Glossary > P

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Packet Switching

The technique by which a stream of data is broken into standardised ‘packets’, each of which contains address, sequence, control, size and error-checking information, in addition to the user data. Packet switches operate on this added information to move the packets to their destination in the proper sequence and again to present them in the correct continuous stream.

PVC – Permanent Virtual Circuit

This is a connection between end points that is defined in advance and needs little, if any, setup time. End points are normally defined for the carrier, by the customer, in advance.

POI – Point of Interface

The point in a network at which carriers interface with one another.

POP – Point of Presence

A long distance company’s switch that’s connected to the local telephone company’s central office. The POP is the point at which telephone and data calls are handed-off between local telephone companies and long distance telephone companies.


The act of moving a telephone number from one network or technology to another one.

POTS – Plain Old Telephone Service

The traditional telephone services for the transmission of speech across the telephone network.

PRI – Primary Rate Interface

This is the narrowband ISDN interface standard for high-speed ISDN service.

PBX – Private Branch Exchange

Equipment used to switch telephone calls within a business or closed environment, and also for that environment to outside lines.

PSTN – Public Switched Telephone Network

The current narrowband-based telephone network that was designed for voice traffic.

PCM – Pulse-Code Modulation

An analogue to digital conversion technique. It’s used to convert voice for transmission over digital facilities. It’s also used to convert voice analogue data to digital data for transmission in a multiplexed voice and data stream, over T1 or other digital circuits.

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