UM380 03 010
105
Glossary of Terms
H
HDB3
High Density Bipolar 3. A coding scheme used across a circuit between
multiplexers.
I
ISDN
Integrated Services Digital Networking. A set of standards and associated
facilities defined by ITU (CCITT), refined for use in Europe by ETSI.
ITU
International Telecommunications Union - new name for the CCITT.
L
LED
Light Emmitting Diode.
LOS
Loss of Signal.
M
MMI
Man-Machine Interface. The presentation characteristics of the operational
interface.
MTBF
Mean Time Between Failures. Can relate to software or hardware faults,
more correctly to all faults. Normally, but not exclusively, used to measure
major faults (i.e. total outage of a subsystem, requiring board replacement
or software reset) rather than transient faults affecting only a subset of the
services (such as a call failure).
MTTR
Mean Time To Return (or Repair or Recovery). Average time for repair/
recovery from a major fault. Does not imply that on-site attendance is
necessary for recovery.
N
NVRAM
Non-Volatile Random Access Memory. Such as battery protected memory or
‘Flash’ memory.
Q
Q.931
An ITU/CCITT standard that specifies a network layer protocol and facilities
for Private and Public digital exchanges.
R
RAI
Remote Alarm Indication. An indication in the channel framing information
on a Primary Rate Interface showing that the equipment signalling the
condition detects a problem in the link or attached equipment.
RAM
Random Access Memory.
ROM
Read-Only Memory.
S
S/W
SoftWare.
T
TCP/IP
Transmission Control Protocol/Internet Protocol. The standard procedure for
regulating transmission on the Internet.
V
Vision iQ
Management Tool (PC application for Windows
®
) for InterChange products.