TM 55-4920-432-13&P
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CONTROLS AND INSTRUMENTS
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a.
General. This section describes and furnishes the operator with sufficient information pertaining to
the various controls and instruments provided for the proper operation of the equipment.
b.
Power Switch. The single pole, double throw, toggle-type power switch, has an OFF position which
opens the circuit and shuts off the electrical power supply to the tester. The ON position is in the
circuit to provide electrical current to the tester when the power source is connected.
c.
Indicator light. The indicator light illuminates when the power circuit in the tester is operating.
d.
Cartridge fuse. The 28vdc, 5amp cartridge fuse provides protection against an excessive flow of
current which would damage the electrical system.
e.
Vacuum Selector Knob. The pressure selector knob has three positions, and operates a valve
which controls the vacuum systems required to test aircraft instruments.
f.
Pressure Selector Knob. The pressure selector knob has three positions and operates a valve
which controls the pressure systems required to test certain types of aircraft instruments.
g.
Pressure Bleed Down Knob. Counterclockwise rotation of pressure bleed knob from closed
position opens a needle valve allowing system pressure to bleed off. CLOSE for pressure up.
h.
Pressure Control Knob. Counterclockwise rotation of pressure control knob from closed position
opens a needle valve allowing pressure in system to increase.
i.
Vacuum Bleed Knob. Counterclockwise rotation of vacuum bleed knob permits system vacuum to
bleed off. CLOSE for vacuum up.
j.
Vacuum Control Knob. Counterclockwise rotation of vacuum control knob opens a needle valve
and provides increased vacuum in system.
k.
Shut-off Valves. Shut-off valves located on the top of the operator panel are provided for testing
aircraft instruments and checking the master instruments for leaks.
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