Technical data

Table 1–3: H7874 Power Supply Switches, Controls,
and Indicators
Control/Indicator Function
AC Present indicator (orange) Lights when the power switch is set to on (1), and the ac
voltage is present at the input of the power supply.
Power switch The power switch is used to turn system power on and
off. The off position is indicated by a 0; the on position is
indicated by a 1.
The power switch also functions as the system
circuit breaker. In the event of a power surge, the breaker
will trip causing the power switch to return to the off posi-
tion (0). Turning the system on resets the circuit breaker.
If the circuit breaker trips, wait one minute before turning
the system back on.
DC OK indicator (green) When the DC OK indicator is lit, the voltages are within
the correct operating range. An unlit DC OK indicator
shows a problem with the power supply.
Fan Failure indicator (amber) The Fan Failure indicator lights if either of the two cooling
fans stops working. The power supply will automatically
shut down the system as a precautionary measure when a
fan failure is detected.
Over Temperature indicator (am-
ber)
The Over Temperature indicator lights if the system has
shut down due to an over temperature condition.
Power bus connectors Three power bus connectors allow you to configure a power
bus for systems expanded with a system expander. The
power bus allows you to turn power on and off for the
system through one power supply designated as the main
power supply: this way, one power switch can control
power for an expanded system (Figure 3–22).
MO The main out connector sends the power control bus signal
to the expander. One end of a power bus cable is connected
here, the other end is connected to the SI (secondary in)
connector of the expander power supply.
SI The secondary in connector receives the power bus control
signal from the main power supply. In a power bus with
more than one expander, the power bus signal is passed
along using the secondary in and out connectors.
SO The secondary out connector sends the signal down the
power bus for configurations of more than one expander.
NOTE: The H7874 power supply automatically selects either 120 or 240 Vac
when power is turned on.
The power supply enters and completes a shutdown sequence whenever the
BPOK H signal is negated. When BPOK H is asserted high on the Q22-
bus, the power system is in a state to allow normal system operation. The
following conditions negate BPOK H:
BA430/BA440 Enclosure Description 1–21