Technical data

Environmental Monitoring
6-15
6
Overtemperature Warning LED
The system thermal warning LED, designated with a thermometer
symbol, can be activated by:
❏ The power supply’s first threshold
❏ High temperature alert from the SCSI peripheral expansion
enclosure.
If disk subsystem is present, signal is available through the
cable from the enclosure’s RJ-45 connector to the back of
control board.
❏ High temperature on the backplane thermal sensors
Backplane sensors (dual 9-, 12-, and 20-slot chassis) are
optional and may not be installed. Backplane sensors are
resistor programmed with plug-in resistors, and therefore the
level could be changed by changing the resistor components.
The sole result of a thermal alarm is that the LED lights.
An optional alarm board is available for use in conjunction with the
environmental monitoring system. The alarm board amplifies
signals from the environmental monitor to make them usable as
inputs to the proprietary alarm systems found at some customer
installations.
Recovery
The surest way to reset the power distribution system after a
shutdown triggered by the environmental monitor is to cycle the
primary power (remove and reconnect the -48Vdc or 115/230Vac
input power).
In systems with a redundant power supply, setting the key switch
to
STANDBY and back to RUN after a thermal or undervoltage failure
restarts the power supply, but requires that the operating system
first be shut down.