Diodes CR1, CR3, CR6 and CR7 comprise an OR gate

TM 11-5820-695-35

3A1P1-33 is open circuit. K1 has no coil voltage and is

(5) The signal 3AlP1-14 comes from the

deenergized.

chassis mounted temperature monitor, thermostatic

switch 3A7S2 (para 2-82), and it is applied to the coil of

relay 3A1K2. This signal is either +28 Vdc (normal) or

(2) If any of the signals at 3AlPl-24, -25, or --

open circuit (fault).

For normal status, +28 Vdc

26 goes to fault status, the corresponding diode CR1,

energizes relay K2, and +28 Vdc through closed

CR3 or CR7 will be forward biased (a(2), (3) and (4)

contacts 82/B1 is applied to AIR FLOW indicator

above). When any OR gate diode (CR1, CR3, CR6, or

3A8DS2 (green). DS2 is lighted. Contact K2-83 is open

CR7) is forward biased, a path to ground (a above) for

and AIR FLOW indicator 3A8DS4 (red) is off. At the

+28 Vdc through R9, R10, and the diode is provided.

same time, +28 Vdc through closed contacts K2-A1/A2

The resulting voltage drop across R9 reduces the

is applied through voltage divider resistors R22 and R23

voltage applied to VR1. VR1 switches to the high

to the cathode of diode CR6. CR6 is reverse biased.

impedance state and cuts off the voltage at the base of

For the fault status, 0 Vdc (open circuit) at 3AlPl-14

Q1. Q1 is then reverse biased; it cuts off and relay K1

causes K2 to be deenergized. Contacts K2-B2/B3 are

is deenergized.

closed and K2-B1 is open. The AIR FLOW red indicator

lights and the green indicator is off. For fault status,

(3) If the signal at 3A1P1-14 goes to fault

closed contacts K2-A2/A3 apply open circuit to R22/R23

status, relay K2 is deenergized (a(5) above). CR6 is

and diode CR6 is forward biased.

then forward biased, Q1 is cut off and relay K1 is

deenergized.

b. Diodes CR1, CR3, CR6 and CR7 comprise an

OR gate. For normal status of the monitored signals,

they are all reverse biased ( a(2) through (5) above).

c. The A-contacts for relay 3AlK1 are used to route

Resistor R10 is then open circuit at the junction with the

the summary alarm signal of unit 3 to orderwire

common anode connection of the diodes. The supply

assembly 1A13 through J22-8 (CONV ALM NORM) and

voltage (+28 Vdc) through R9, VR1, and R11 turns on

J22-C (CONV ALM FLT). Three combinations of logic

VR1 (low impedance state) and forward biases transistor

signals at J22-B and -C are used to indicate the

Q1. Relay K1 has +28 Vdc applied to the coil (a(1)

normal/fault status of unit 3 and the operating mode of

above) and Q1 is forward biased, so for normal status,

AN/GRC-144(V)4. They are shown in the chart below,

K1 is energized. Closed contacts K1-B1/B82 apply +28

along with all operating conditions associated with each

Vdc through 3A1P1-32 and cause ALARM SUMMARY

state. Chassis mounted relay 3A7K1 is used with relay

indicator at 3A8 to light green (normal). Relay K1 will

3AlKl to generate these status signals. The signal at

be deenergized if the +28 Vdc coil voltage is cut off or if

J22-A is always logic 0 (ground); this signal is connected

Q1 is cut off. When K1 is deenergized, closed contacts

through 3AlPl-36 to 3A1K1-A2. The coil of relay 3A7K1

K1-B2/B3 apply +28 Vdc through 3A1P1-12 and cause

is connected to 322-A (ground) and to J22-E. For C-

ALARM SUMMARY indicator to light red (fault). Relay

band operating mode, the signal at J22-E is +28 Vdc

K1 is deenergized if any one of the five monitored

and relay 3A7K1 is energized. For K-band operating

signals goes to fault status.

mode, the signal at J22-E is 0 Vdc (open circuit) and

relay 3A7K1 is deenergized. The chart on the following

(1) If the temperature in 3A5 is out of normal

page indicates the logic status of the summary alarm

range, the signal at

signals and the signal routing for all operating

conditions.

Change 6 2-140