Compartment Differential Pressure Switch (fig. 1-45).
The compartment differential pressure switch is located in the crew
The switch has a round disc-like shape with two
pneumatic ports and an electrical connector with three pins.
compartment; the other port, the low-pressure port, connects to a
line that leads outside the crew compartment.
The switch senses the pressure differential
between the inside and outside of the crew compartment. If
the pressure difference reaches less than 1.5 inches of
water or 0.07 psi, the switch turns on the "CREW PRESSURE
LOW" light on the commander's control panel.
turns the light off when the pressure differential
increases to 2.0 inches of water or 0.06 psi.
If the switch sticks on contact "A," the
light stays off at all times when the system operates, and
if the switch sticks on contact "B," the light stays on at
all times when the system operates.
If the diaphragm
ruptures, the light stays on.