Appendix D - Glossary
150-359-100-01, Revision 01
56
October 27, 2000
HXU-359 List 1
A
PPENDIX
D - G
LOSSARY
AIS
Alarm Indication Signal — An all ones signal generated to
replace the normal traffic signal when it contains a defect
condition. Used to prevent consequential downstream failures
being declared or alarms being raised.
ALM
Alarm
AMI
Alternate Mark Inversion
APS
Automatic Protection Switching — Installing a redundant HXU
provides a standby in the event the active HXU fails.
B8ZS
Bipolar with 8-zero Substitution
BER
Bit Error Rate — The number of coding violations detected in
a unit of time, usually 1 second.
BER = errored bits received
÷
total bits sent.
BIP
Bit-interleaved Parity — A parity check that groups all the bits
in a block into units (such as a byte), then performs a parity
check for each bit position in a group.
BLER
Block Error Rate — Blocks in which one or more bits are in
error. BLER = errored blocks received
÷
error blocks sent.
BPV
Bipolar Violation
CI
Customer Interface
CO
Central Office
CPE
Customer Premises Equipment
CRC
Cyclic Redundancy Check — A technique for using overhead
bits to detect transmission errors.
CSA
Carrier Serving Area
CV
Code Violation — A transmission error detected by the
difference between the transmitted and the locally calculated
bit-interleaved parity.
DCC
Data Communications Channel — Bytes in the SONET
overhead that are used to provide a communication channel
between SONET network elements.
DCE
Data Communications Equipment
DCS
Distributed Communications System
