363-206-305
Circuit Pack Descriptions
7-42
Issue 3 June 2000
When a T1EXT circuit pack is inserted, the relays are in the protection state until
the SYSCTL determines that the circuit pack is good.
The BBF6 T1EXT circuit pack can be mixed with the BBF1/1B. If mixed, the
protection circuit pack must be a BBF3 DS1PM circuit pack.
Fault Detection Circuitry
7
The T1EXT circuit pack has in-service and out-of-service built-in test capability. In-
service testing is continuous and errors are reported when they occur to the
SYSCTL via the intra-shelf control bus. An out-of-service test is performed
whenever the T1EXT circuit pack is inserted or recovers from a transient failure.
The incoming DS1 signal is monitored for bipolar threshold crossings in excess of
10
-3
, 10
-6
, 10
-7
, or 10
-8
. Incoming VT1.5 signals are monitored for VT AIS, VT LOP,
and yellow.
Loopbacks
7
The T1EXT circuit pack provides a terminal loopback for testing. The terminal
loopback is provided on the T1EXT circuit pack for each DS1 low-speed interface.
The loopback is implemented inside the MUX/DEMUX/DESYNC device and
bridges the desynchronizer output signal (transmitted toward the T1 line) back into
the DS1 synchronizer input. When the loopback is operated, the DS1 interface
device forces AIS toward the DSX.
Performance Monitoring
7
The T1EXT circuit pack provides PM circuitry for the following performance
parameters:
â–
VT path parameters derived from V5 coding violations
â–
T1EXT PM derived from SF/ESF frame format depending on provisioning.
Power Circuitry
7
The OLIU circuit packs supply +5 V power to the T1EXT circuit packs. These
inputs are diode ORed and the output is fused and then filtered before it is used to
power the rest of the circuit pack. A failure of the fuse causes the red FAULT LED
to light.
The T1EXT also simplexes 60mA constant current on the line for powering a CSU
at the far end/or provides sealing current for the line.
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