AT&T MERLIN LEGEND System Reference Manual page 639

Glossary
Primary Rate Interface (PRI)
A standard Integrated Services Digital Network (ISDN) access interface that specifies the protocol used between two or more
communications systems. PRI runs at 1.544 Mbps and, as used in North America, provides twenty-three 64-kbps B channels
(voice or data) and one 64-kbps D channel (signaling). The D channel is the 24th channel of the interface and contains
multiplexed signaling information for the other 23 channels.
prime line
An individual extension number assigned to a telephone in a Behind Switch system. Each telephone user has his or her own
prime line and is automatically connected to that line when he or she lifts the handset.
processor module
The module in the second slot of the basic carrier that contains the software that runs the communications system.
protocol
A set of conventions governing the format and timing of message exchanges between devices, such as a multiline analog
telephone and the communications system control unit.
public network
A network that is commonly accessible for local or long-distance calling. Also called public switched telephone network
(PSTN) .
pulse amplitude modulation (PAM)
A modulation technique in which an analog signal, such as speech, modulates a carrier signal consisting of a series of
precisely timed pulses of equal amplitude. See also pulse code modulation.
pulse code modulation (PCM)
An extension of pulse amplitude modulation (PAM) in which each PAM pulse is quantized and encoded into a 8-bit code to
represent the amplitude of each PAM pulse. See also pulse amplitude modulation.
Q
quantizing
The process of converting a pulse amplitude modulation (PAM) sample into a discrete number of amplitude values.
R
RAM Random access memory)
Computer memory in which an individual byte or range of bytes can be addressed and read or changed without affecting
other parts of the memory.
riser cable
Cable that runs between floors in a multistory building and connects wire closets.
robbed-bit signalling (RBS)
Signaling in which the least significant bit (LSB) of every sixth frame per channel is used for signaling in that channel.
ROM (read-only memory)
Computer memory that can be read but cannot be changed.
RS-232
A physical interface, specified by the EIA (Electronics Industries Association), that transmits and receives asynchronous data
at speeds of up to 19.2 kbps over cable distances of 50 feet.
GL-12 Glossary