Circuit Pack Descriptions
Issue 8.0 July 2002
7-121
reference is not equipped or fails, the TG3 (DS1) circuit pack will attempt to select
the secondary DS1 reference (if equipped). If all four of these references fail, the
TG3 (DS1) circuit pack will enter the holdover mode.
In the through timed mode, if both line references fail, the TG3 (DS1) circuit pack
will enter the holdover mode.
Fault Detection Circuitry 7
The TG3 (DS1) circuit pack has an in-service and out-of-service built-in test
capability. In-service testing is continuous and errors are reported when they
occur to the LNCTL circuit pack via the BCLAN. An out-of-service test is
performed whenever the TG3 (DS1) circuit pack is inserted in a slot or reset.
The TG3 (DS1) circuit pack also monitors the incoming DS1 timing reference
signals for the following:
■ Loss of signal (175 ±75 consecutive zeros)
■ DS1 alarm indication signal (AIS) for at least 125 µsec
■ Bit error rate (BER) greater than 2x10
-4
for a period ≥ 3 seconds
■ Loss of frame for a period ≥ 3 seconds
■ Excessive out-of-frame count
■ Clock frequency out of specifications.
If one TG3 (DS1) circuit pack detects an incoming DS1 reference failure, it will
signal the LNCTL circuit pack. The LNCTL circuit pack signals the companion
TG3 (DS1) circuit pack to accept the secondary DS1 reference signal.
Power Circuitry 7
The TG3 (DS1) circuit pack receives two sources of −48 volts that are diode OR'd,
fused, and filtered. A modular DC-to-DC power converter produces +5, −15, and
+15 volts used on the circuit pack.
The TG3 (DS1) circuit pack monitors the two −48 volt sources to the circuit pack
and any failures are reported to the board controller. If the TG3 (DS1) circuit pack
detects a failure of the onboard fuse or power converter, the red FAULT LED will
light. If the fuse or +5 volt power converter fails, the LNCTL circuit provides +5
volts to light the FAULT LED on the TG3 (DS1) circuit pack.
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