List of terms 79
ISDN Primary Rate Interface.
Private Branch Exchange
PBX; A small telephone switching center enabling a customer’s telephone
stations to connect to the public switched network.
Private Exchange
A private (manual) telephone exchange that provides private telephone
service to an organization that does not allow calls to be transmitted to or
from the public telephone network.
PROPvl
Programmable Read-Only Memory.
Public Switched Network
The Direct Distance Dialing (DDD) telephone network; Any exchange type
of service that is made available for public use.
. .
Pulse Code Modulation (PCM)
A modulation technique whereby the signal is converted from an analog to
digital format by sampling the signal at periodic intervals and digitizing the
amplitude into a finite number of discrete levels; Five-bit information code.
RAM
Random Access Memory; Storage system or computer memory that is
accessible by the user for either storing or retrieving information. RAM is
volatile memory.
Redundancy
The duplication of software/hardware used as a standby in case one fails
(redundant CPUs).
Retrofit
To furnish with new parts or equipment not available at the time of
manufacture.
RF
Radio Frequency; A group of electromagnetic energy waves whose lengths
are between the audio range and the light range.
System overview 553-3001-100