363-206-285
Power
Issue 3 June 2001
4-5
LEDs 4
Two green power on (PWR ON A and B) on Group 4 shelves or a single PWR ON
on Group 1 and Group 3 shelves
—LED(s) on the user panel—indicate that the
shelf is receiving fused −48 volt power. The LED will remain illuminated as long as
either −48 volt feeder is supplying power to the shelf.
Normally the FAULT LED on the circuit pack faceplates is operated via the
controller which provides a ground return for current generated by the on-board
converter. In the event of a DC-to-DC converter failure, the LED will be operated
via the −48 volt power leads. The −48 volt power leads are supplied through an
electronic gate or relay contact normally held open by the converter. The power,
fusing, and LED circuits shown in Figure 4-2 are used on all circuit packs with on-
board DC-to-DC converters.
Figure 4-2. Circuit Pack Power and LED Control
Power Minor Alarm 4
A yellow power minor (PMN) alarm LED is provided on the user panel to indicate
an AC power failure at the remote terminal. The PMN alarm can be provisioned by
aswitchontheSYSCTLcircuitpackatthecentraloffice(CO)tobeeitheran
office minor (MN) or office major (MJ) alarm.
&
RTN RTN
Diode
ORing
Current
Limiter
Fuse
Filtering
LED Control
Fault LED
(Red)
-48 V -48 V
DC/DC
GND
Converter
Relay
+5 V
&
RTN
-48 V (A)
-48 V (B)
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