Continuity Self-Test Resistors.

TM 55-4920-430-13

(8) Capacitor C11 is charged thru resistor R52 and U5 for an rc time constant of 1.21 second. Ca-

pacitor C11 is discharged thru a 10K ohm resistor in U5 and transistor Q3, for a time constant of 10

US. The time for capacitor C11 to charge to 1.4 volt dc is 0.33 second. Since the period of the 7 Hz dash

drive signal is 0.143 second, the long charging time constant of capacitor C11 inhibits turning off the

DASH drive lamp between the 7 Hz pulses.

d. Continuity Self-Test Resistors.

(1) Resistor R44 is connected across connector pins J1-48 and J1-14. It is the nominal 1.5-ohm

(2) Resistor R45 is connected across connector pins J1-44 and J1-13. It is the nominal 0.5-ohm

e. Logic Stimulus signals.

(1) The output at pin 4 of inverter U6 is connected to connector pin J 1-12. The output is used as a

TTL logic 1 voltage with a nominal level of 4.5-volt dc.

(2) The RAD-ALT-S/T signal from connector pin J1-11 is applied to pin 1 of inverter U6. U6

provides an inverted TTL logic output on connector pin J1-47. When connector pin J 1-11 is an open

circuit, the output from inverter U6 at connector pin J1-47 is 0-volt dc (logic 0). When connector pin

J1-11 is connected to ground at connector pin J1-21, the ouput from inverter U6 at connector pin J1-47

i s 4.5-volt dc (logic 1).

(3) When the output at pin 2 of inverter U6 is high, the output at pin 8 of inverter U6 is low. With

a low at pin 8, relay K3 is activated.

1-29/(1-30 blank)