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packet

A logically grouped unit of data of a fixed size that has been prepared for network transmission. A packet typically contains header information (consisting of its origin, its destination, and synchronization information) and payload data. See also payload.

packet-switched network

A network in which data transfer and signaling is accomplished by sending discrete packets from host to host. No effort is made to establish an electrical circuit between two computers. Each packet contains its original address and the address of its destination. Data from many different sources can be transmitted on the same lines, and be sorted and directed to different routes by special machines along the way. See also circuit-switched network, connectionless, packet.

parameter

A variable that dictates the behavior of functions.

parameter structures

Multiple parameters that are grouped together in C language structures.

pattern

In telephony, a repeated 8-bit sample applied to an output terminus of a switch block using messaging mode.

payload

The data in a packet or message structure, not the system overhead information such as addressing, control, or header information. See also header.

PBX or PABX

Private (Automatic) Branch telephone eXchange; a system providing local telephone switching in an office or building.

PCI

Peripheral Component Interconnect; a 32/64 bit local bus inside a PC. See also CompactPCI.

PCM

Pulse Code Modulation; a digital scheme for transmitting analog data. The signals in PCM are converted into binary data, which is then transmitted digitally.

pending command

A command that has been sent from the host to the hardware, but has not yet been acknowledged by the hardware returning its associated event.

.pf file

Parameter definition file; used to automatically generate parameter source and header files.

pf2src

Utility used to convert a .pf file to parameter source and header files.

Phase A

The call setup phase of a T.30 protocol fax session. See also Group 3 fax, T.30.

Phase B

The pre-message procedure for identifying and selecting call-specific facilities of a T.30 protocol fax session. See also Group 3 fax, T.30.

Phase C

The image transfer phase of a T.30 protocol fax session. See also Group 3 fax, T.30.

Phase D

The post-message procedures (EOM and multi-document procedures) of a T.30 protocol fax session. See also Group 3 fax, T.30.

Phase E

The call release phase of a T.30 protocol fax session. See also Group 3 fax, T.30.

physical layer

In the OSI layering model, the physical layer (layer 1) is the electrical and mechanical layer. Protocols for this layer describe, on an electrical and mechanical basis, the methods used to transfer bits from one device to another. One protocol used at this layer in ISDN is CCITT recommendation I.430/I. See also data link layer, end-to-end layers, layer, network layer, Open System Interconnect (OSI).

PICMG

PCI Industrial Computer Manufacturers Group; an industry consortium which defined the CompactPCI standard, and other technical specifications such as hot swap. See also CompactPCI, hot swap.

ping

Packet InterNet Groper; an application that verifies one host's ability to reach another host over a network.

point

An interface between ISDN equipment categories.

point code

A unique address assigned to each signaling point in an SS7 network. The ITU-T variant of MTP uses a 14-bit point code. The ANSI variant of MTP uses a 24-bit point code.

Point-to-Point Switching service

CT Access service that provides an API for making switch connections between boards. The Point-to-Point Switching service enables an application to make switch connections without needing to specify stream and timeslots assignments. See also connection, listener(s), talker, timeslot.

polling

During a fax polling operation, the calling fax terminal requests that the called fax terminal send documents to the calling fax terminal. This is also known as turnaround polling.

port

A point of connection, such as:

• An external connection between the MVIP bus and anything else, including telephone trunks, human operators, voice processors, fax processors.
• A logical channel in a communications system, usually associated with physical hardware resources.
• A point of connectivity between a computer and anything else, such as telephone trunks, human operators, voice processors, or fax terminals.
• In Internet transport protocol, refers to the abstraction used to distinguish between multiple simultaneous connections to a single destination host. A port is a transport layer demultiplexing value. Each TCP/IP application has a unique port number associated with it.
• Refers to a logical entity on a DSP board which can run telephony protocols, play and record voice files, or execute other DSP functions. It is typical to connect such a DSP port to a line interface or a trunk by using MVIP switching. This type of port generally corresponds to a CTA context in the ADI service.
• Refers to telephone connections supported by a board (for example, the AG 2000 board is an 8-port board).

PPX configuration file

In the CT Access Point-to-Point Switching service, the file that specifies the switch configuration for a system.

PPX server

The Point-to-Point Switching service server process, ppxserv. It maintains an internal connection database to monitor timeslot availability and timeslot assignments on the system's telephony bus. It is used by each instance of the Point-to-Point Switching service (each instance is PPX client).

PRI

Primary Rate Interface; a term used to describe a trunk configuration consisting of 23 B channels and one D channel running at 1.544 Mbyte/s (or 30 B channels and one D channel at 2.048 Mbyte/s in Europe). It is an ISDN interface equivalent to a T1 circuit. Also known as primary rate. See also ISDN.

PRI (Group 3 fax)

PRocedure Interrupt; a signal to the remote fax terminal which requests the remote fax terminal to permit operator interaction. A PRI signal is used to request that the remote fax terminal allow operator intervention, such as voice communications over the handset, and not hang up the call at the end of a fax session.

primary [clock] master

An MC1 board which synchronizes to the primary MVIP MC1 clock mode. The MC1 board references the MVIP bus to drive the left or right clock signals. See also clock master, left clocks, MC1 board, MVIP, right clocks.

primitive

A low-level function or operator which is built into a programming language or operating system.

In AG ISDN, messages used by a layer to request services from an adjacent lower layer.

An abstract, implementation-independent representation of an interaction; in the OSI protocol layering model, a layer requests services from an adjacent lower layer using primitives.

prompt

A voice message, typically a short message used in a menu, guiding the user to perform a task or choose an option. See also message.

protocol (telephony)

Defined procedure for call setup and call teardown.

protocol-independent

Consistent for all available protocols.

protocol stack

The AG ISDN protocol stack; software running on the AG board which implements OSI layer functionality. The ISDN protocol stack can run in NCC configuration, ACU configuration, or LAPD configuration, depending upon how the application is to access the ISDN protocol stack. See also ACU stack mode, ISDN, LAPD stack mode, NCC stack mode.

PSTN

Public Switched Telephone Network; a public telephone network.

Pulse Code Modulation

See PCM.

pulse dialing

The method used on rotary-dial telephones to signal a telephone number for automatic switching. Each digit is encoded as a series of one to ten pulses, which are brief interruptions of current flow on the line. See also DTMF.

pulse width

The time during which a network tone is active.

Pulsed E and M

A telephone signaling system used between two switches that uses two wires called the E lead and the M lead. In analog E and M, the M lead of one switch is connected to the E lead of the other, and vice versa. In digital E and M signaling, a single bit is used to convey signaling states. A common mnemonic is that E stands for ear-lead and M for mouth-lead. See also E&M.