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Circuit Pack Descriptions
7-88 Issue 3 June 2001
Fault Detection Circuitry 7
The BBG19 DS3 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 BBG19
DS3 circuit pack is inserted or recovers from a transient failure.
The incoming DS3 signal is monitored for bipolar threshold crossings in excess of 10
-3
or 10
-6
, LOS, DS3 OOF, and DS3 AIS. Incoming STS-1 signals are monitored for STS
AIS, STS LOP, and yellow and are also monitored for DS3 OOF and AIS.
Loopbacks 7
Two loopbacks are provided on the BBG19 DS3. The terminal loopback bridges the
DS3 desynchronizer output signal (transmitted towards the data services device) back
into the DS3 synchronizer input. Operation of the loopback does not affect the signal
transmitted to the data services device. The facility loopback bridges the STS-1 output
signal to the OLIU back towards the data services device. Operation of this loopback
does not affect the signal transmitted to the fiber. Both loopbacks are controlled by the
SYSCTL through the intra-shelf control bus.
Performance Monitoring 7
The BBG19 DS3 circuit pack provides PM circuitry for the following performance
parameters:
â– STS path parameters derived from B3 coding violations
â– DS3 path parameters derived from P-bit coding violations
â– DS3 path parameters derived from F&M bit errors
â– DS3 line errors based on B3ZS violations
â– DS3 P-bit and F&M bit PM for both directions of transmission
â– C-bit parity and FEBE PM for both directions of transmission.
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