Glossary
Glossary-7
3360-A2-GB20-20
December 1996
parity
A way of checking data accuracy by counting the number of bits that have a value
of one.
payload
The information bits in a frame.
PBX
Private Branch Exchange. Telephone switching equipment dedicated to one
customer. A PBX connects private telephones to each other and to the public
network.
PC
Personal computer. In this document, references to a PC imply an IBM PC or an
IBM-compatible PC.
PDU
Protocol Data Unit. Used when adding routes in the Internet.
PDV
Pulse Density Violation. The number of “ones” (marks, pulses) is not adequate for
the line requirement.
Perf branch
Performance Report branch of the E1 NTU menu tree.
PLB
Payload Loopback. Loops the received signal on the network interface back to the
network after it has passed through the framing circuity of the E1 NTU.
port
An access point for data entry or exit.
PORT (1– 4) interface
The synchronous data port interface on the E1 NTU.
POWER connector
The power input connector on the E1 NTU.
power-up self-test
A test that checks most hardware components when power is applied to the device
or a reset is initiated.
PPP
Point-to-Point Protocol. A link layer protocol used by SNMP.
PRBS
Psuedo-Random Bit Sequence. A test pattern containing any possible combination
of digital ones and zeros for a given string length.
primary clock
The primary timing source used to synchronize all of the E1 and data port interfaces
on the E1 NTU.
PRM
Performance Report Message. A message indicating performance data such as
errored seconds, unavailable seconds, etc.
protocol
A set of rules that determines the behavior of functional units in achieving
communication.
Ptrns branch
Test Patterns branch of the E1 NTU menu tree.
pulse density
A measure of the number of “ones” (marks, pulses) in relation to the total number
of bits transmitted.
QRSS Test
Quasi-Random Signal Test. A test pattern simulating a random pattern of digital
ones and zeros used to simulate normal transmission.
RAI
Remote Alarm Indication. A remote alarm on an E1 line.
RAM
Random-access memory. Read/write memory that is volatile and loses its contents
when power is removed.
register
A part of the device’s memory that holds stored values.
Rel branch
Release branch of the E1 NTU menu tree.
