Click on an index letter to navigate through our glossary terms:
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P-LINE (PRIVATE LINE)
A non-switched line that connects one single telephone directly to another. It is not connected to the public network. -
PABX (PRIVATE AUTOMATIC BRANCH EXCHANGE)
See PBX. -
PARALLEL TRANSMISSION
A method of sending information whereby all the bits of a byte are sent at the same time over separate wires, as opposed to sending all the bits sequentially over a single wire (SERIAL TRANSMISSION, see also). -
PBX (PRIVATE BRANCH EXCHANGE)
The word exchange was used for the equipment that was used at the telephone company, back when the operator used to connect all of the calls manually and there was a direct line from every telephone set to the central office. As the need for service increased, the need for equipment that would handle more than one line was demanded. The telephone company sold an "exchange" that could be used at a private company that was a branch of the telephone company exchange. The whole name of the system was and is a PRIVATE BRANCH EXCHANGE. It allowed a company to have its own manual operator and to extend any incoming trunk to any station on the system, thus allowing for many telephone sets to share a smaller number of trunks. -
PC (PERSONAL COMPUTER)
Usually used in reference to an IBM compatible computer, but can refer to any desktop-sized or smaller computer that generally handles only one user at a time -
PCM (PULSE CODE MODULATION)
The most common method for converting analog voice signals into digital signals, for use in transmission over digital phone lines (such as T-1s) and in digital recording of voice. -
PEG COUNT
The number of attempts on a circuit. -
PORT
An analog or digital inlet or outlet to the system. The trunks and stations of a PBX are usually connected to ports. Also, a device which the computer uses to communicate with some device, such as a printer or a mouse -
POTS (PLAIN ORDINARY TELEPHONE SERVICE)
Basic telephone service utilizing single-line phones to connect to the public switched network with no added features. Uses LOOP START (see also) signaling. -
PREFIX
A code for a central office in the North American Numbering Plan. Also known as NXX. See also EXCHANGE NUMBER -
PREMISES (PREM)
The space occupied by a customer or authorized user in a single building or in connecting buildings not separated by a public highway. -
PRI (PRIMARY RATE INTERFACE)
A flavor of ISDN that is carried on a T-1 circuit. It provides 23 B-CHANNELs (see also) and one D-CHANNEL (see also) for signaling. -
PSAP (PUBLIC SAFETY ANSWERING POINT)
The facility that takes incoming 911 calls and dispatches emergency response teams or hands the calls off to the appropriate agencies. -
PUC (PUBLIC UTILITIES COMMISSION)
A state agency that is in charge of regulating phone companies as well as other utility companies in the state.