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Circuit Pack Descriptions
7-38 Issue 3 June 2001
Fault Detection Circuitry 7
The DS1PM 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 DS1PM 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 DS1PM circuit pack has two loopback types: terminal and facility. Both
loopbacks are controlled by the SYSCTL via the intra-shelf control bus. The two
loopbacks must be done independently.
A terminal loopback is provided on the DS1PM 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 DS1PM 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.
The new BBF3B DS1PM circuit pack also has single DS1 facility loopback
capability. The loopback, however, is not a bridge and AIS will be transmitted
toward the high-speed interface. This feature requires Release 13.0 or higher.
The circuit pack is backwards compatible and can be used in place of the BBF3.
Performance Monitoring 7
The DS1PM circuit pack provides PM circuitry for the following performance
parameters:
■ VT path parameters derived from V5 coding violations
■ DS1 PM derived from SF/ESF frame format depending on provisioning.
Power Circuitry 7
The MXRVO/STS1E circuit packs supply +5 V power to the DS1PM circuit packs
in the corresponding DS1PM circuit pack groups. 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 or converter causes the red FAULT LED to light.
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