Avaya 1000 Series, Reference

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Microprocessor
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 266: 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
Architecture
Circuit Card Reference July 2011 657