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Circuit Pack Descriptions
Issue 1 December 1997 7-9
Power Monitoring and Fan Control 7
The SYSCTL monitors the two −48 volt feeders and generates an alarm if one
fails. It also monitors AC power in a remote terminal application via a power minor
alarm input closure and can control the external fan, based on an on-board
temperature sensor. The system also monitors the fan control relay for contact
failure.
If the voltage to the shelf drops below the safe operating voltage, the system will
suspend normal operations and wait for safe operating voltage to return. This is
referred to as "brownout protection." Assuming a sufficient voltage level, an "L" will
be displayed on the SYSCTL. The BBG8 operates in integrated grounding
(-48VRTN connected to frame ground) architecture systems. The BBG8B
operates in either integrated or isolated grounding (-48VRTN not connected to
frame ground) architecture systems.
Interface to Other DDM-2000 OC-12 Shelves 7
The SYSCTL interfaces with SYSCTLs of other DDM-2000 OC-12 shelves
through intershelf cabling. This interface allows the user to access each
DDM-2000 OC-12 shelf in a bay via a modem or craft interface terminal (CIT)
connected to any shelf in that bay.
Power Circuitry 7
The SYSCTL receives two sources of −48 volts which are diode ORed, fused, and
filtered prior to conversion to a +5 volt source to power the rest of the circuit pack.
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