APPENDIX
Glossary E-1
E
Glossary
A
A-bit (active bit)
The bit in the frame relay frame header that indicates the status of the far end user device and the
status of the PVC segment in the foreign network.
A-law
An analog to digital encoding scheme used to convert voice samples to an 8-bit data word used
in CEPT E1 multiplex equipment. (See also -law.)
ABR (Available Bit Rate)
ATM connection type for bursty traffic, such as data. Provides closed loop control of service rate
that allows connections to use additional bandwidth when available. ABR may be used with ATM
Traffic Management 4.0 standards VSVD flow congestion control, or with the proprietary
ForeSight flow congestion control. (See also CBR and VBR.)
ACO (Alarm Cut Off)
A switch to turn off the audible alarm outputs from a node while leaving the visual alarm outputs
unchanged.
adaptive voice
An optional feature of the IPX switch that disables VAD from connections using it whenever
there is excess bandwidth available to allow the normal encoded voice to be carried on the packet
line. (See also VAD.)
ADPCM (Adaptive Differential Pulse Code Modulation)
A compression method that samples voice 8,000 times per second, and uses the changes between
samples as the basis for compression. Increases the capacity of a T1 line from 24 to 48 channels.
ADTF (Allowed Cell Rate Decrease Factor)
Time permitted between sending RM cells before the rate is decreased to ICR.
AIT (ATM Interworking Trunk Card)
The AIT front card provides an ATM trunk interface for the IPX switch. The AIT operates in
conjunction with a backcard, AIT-T3 or AIT-E3.
AIT-E3 (ATM Interworking Trunk E3 Interface Card)
The AIT-E3 backcard provides an E3 interface for the AIT (IPX switch) or BTM (IGX switch)
ATM trunk cards.
