Illumination of this light indicates that the radome is inflated to a safe pressure. A pressure transducer, MT1, in the
radome-platform, which is essentially a variable potentiometer, has its wiper connected through resistors R3 and R4 to a
pressure gauge on the Antenna Control Power Supply. The function of this circuit is to indicate the radome pressure in
pounds per square inch. The pressure transducer varies its resistance with radome pressure. The pressure gauge is
essentially a 0- to 100-microampere, graduated from 0 to 1, representing pounds per square inch from 0 to 1. With zero
radome pressure, the movable arm of the pressure transducer is positioned so that there is no current flow through the
meter and the needle on the meter is at 0. As radome pressure increases, the current through the meter increases,
causing the deflection of the needle on the meter to increase. The pressure gauge is adjusted by potentiometers R3 and
R6 so that when radome pressure is zero, the needle is at 0 and when radome pressure is 1 PSI, the needle is at 1.
(3) DEICER CIRCUITS (See Figure 1-10) - The radome-platform deicer circuits consist of RADOME POWER
circuit breaker CB1 and the DEICER switch on the Antenna Control Power Supply. When the radome circuit breaker is in
the ON position, three-phase AC power is made available to contacts of relay K3 in the radome-platform. The deicer
switch on the Power Supply controls operation of relay K3. This switch is in series with pressure switch S4 and
temperature switch S5 in the radome-platform. Should radome pressure fall below 9 inches of water (approximately 0.
35 PSI) or the temperature in the radome increase to 38 degrees Fahrenheit, the switches will open, automatically
shutting off the deicers. Assuming sufficient operating pressure at a temperature below 38 degrees Fahrenheit with the
deicer control switch on the Power Supply in the ON position, phase A from the primary power source energizes relay K3,
supplying one phase of the primary power source to a bank of three heat lamps.
(4) UTILITY CIRCUITS - The utility circuits in the radome-platform consist of two convenience outlets and a
power switch on panel Al and two work lights. Primary operating power for the utility circuits is obtained through the
UTILITIES circuit breaker, CB2, on the Antenna Control Power Supply.
(5) INTERCOM CIRCUIT - The radome-platform intercom circuit consists of head and chest set jack, J14, on
the junction box in the radome platform. This jack is connected through the antenna pedestal to a PHONE jack J6 on the