363-206-285
Power
4-4 Issue 3 June 2001
"A Group" receive power from the MXRVO/STS1E packs mounted in the "A" Function
Unit slots. The "B" and "C" DS1/DS1PM/HDSL circuit packs likewise receive +5 volt
power from the MXRVO/STS1E circuit packs in the "B" and "C" Function Unit slots. Both
MXRVO/STS1E circuit packs in a protection pair supply power to the DS1/DS1PM/HDSL
packs. Power selector circuits (diode ORed) and fuses for the +5 volts are located on the
DS1/DS1PM/HDSL circuit packs. The fuses on the DS1/DS1PM/HDSL circuit packs
protect the backplane and prevent DS1/DS1PM/HDSL unit failures from affecting service
in the other DS1 units or MXRVO/STS1E units within the group.
The power selector circuits on the DS1/DS1PM/HDSL/LAN circuit packs automatically
select power from either MXRVO/STS1E circuit pack. Each MXRVO/STS1E power
converter can support the load of all DS1/DS1PM/HDSL circuit packs in the group (a
condition that occurs if there is an MXRVO/STS1E circuit pack failure).
NOTE:
If any DS1PM/HDSL/LAN circuit packs are used in a Function Unit group, both
Function Unit slots must be equipped with MXRVO/STS1E circuit packs.
Requirements for equipping both Function Unit slots prevent the potential for
continued loss of service after a shelf power failure and subsequent power
recovery.
Removal of a single MXRVO/STS1E circuit pack is allowed during maintenance
activities (for example, circuit pack failure and replacement) and a non-service-
affecting alarm will be activated until the removed circuit pack is replaced.
Control Circuit Packs 4
The SYSCTL and OHCTL circuit packs are each powered by a −48 volt to +5 volt DC-to-
DC converter located on the pack. The backplane power feeders supply A and B −48 volts
to these converters via diode ORed circuits and fuses mounted on the circuit packs.
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