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Circuit Pack Descriptions
7-30 Issue 3 June 2001
Fault Detection Circuitry 7
The DS1 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 DS1 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
or 10
-6
. Incoming VT1.5 signals are monitored for VT AIS, VT LOP, and yellow.
Loopbacks 7
The DS1 circuit pack has a DS1 terminal loopback controlled by the SYSCTL via
the intra-shelf control bus.
The terminal loopback is provided on the DS1 circuit pack for each DS1 low-
speed interface. The loopback is done inside the MUX/DEMUX/DESYNC device
and bridges the desynchronizer output signal (transmitted towards the DSX-1)
back to the DS1 synchronizer input. When the loopback is operated, the DS1
interface device forces AIS towards the DSX-1.
The DS1 circuit pack also provides a facility loopback for all four DS1 signals
(Release 9.1 and later) on a circuit pack. When this loopback is completed, all four
DS1 signals received from the DSX are simultaneously looped back toward the
DSX. The loopback is a bridge, so the transmitted DS1 signals (towards the high-
speed interface) are not affected.
Performance Monitoring 7
The DS1 circuit pack monitors VT path parameters derived from the V5 coding
violations.
Power Circuitry 7
The MXRVO/STS1E circuit packs supply +5 V power to the DS1 circuit packs in
the corresponding DS1 circuit pack groups. These two 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 or converter causes the red FAULT LED to light.
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