Nortel Networks Circuit Card 311 - Manual (Page 1070)

1070 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 435
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 01.04 Standard
Release 5.0 23 May 2008
Copyright © 2003-2008, Nortel Networks
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