Owner's manual

970 NTRB21 DTI/PRI/DCH TMDI card
The NTRB21 is equipped with bit-slice microprocessors that handle the
following major tasks:
•
Task handler: also referred to as an executive. The task handler
provides orderly per-channel task execution to maintain real-time task
ordering constraints.
• Transmit voice: inserts digital pads, manipulates transmit AB bits for
DS1, and provides graceful entry into T-Link data mode when the data
module connected to the DTI/PRI trunk is answering the call.
• Receive voice: inserts digital pads and provides graceful entry into
T-Link data mode when the data module connected to the DTI/PRI
trunk is originating the call.
•
T-Link data: a set of transmit and receive vectored subroutines which
provides T-Link protocol conversion to and from the DM-DM protocol.
• Receive ABCD filtering: filters and debounces the receive ABCD bits
and provides change of state information to the system.
•
Diagnostics
•
Self-test
Digital pad
The digital pad is an EPROM whose address-input to data-output transfer
function meets the characteristics of a digital attenuator. The digital
pad accommodates both µ255-Law and A-Law coding. There are 32
combinations each for µ255 to µ255, µ255 to A-Law, A-Law to µ255, and
A-Law to A-Law. These values are selected to meet the EIA loss and level
plan.
Table 406
Digital pad values and offset allocations
Offset
PAD set 0 PAD set 1
0
0dB –7db
1
2dB –8db
2
3dB –9db
3
4dB –10db
4
5dB 0.6db
5
6.1dB 7db
6
8dB 9db
7
–1dB 10db
8
–3dB 11db
9
–4dB 12db
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 02.06 Standard
27 August 2008
Copyright © 2003-2008 Nortel Networks
.