Figure 2-10. Summing Circuits in Speaker & Headset Amplifier Inputs

TM 11-5895-1141-34

high frequencies. The output of operational amplifier U5 is then coupled via SPEAKER VOLUME control resistor R50,

which provides for a 20 dB signal reduction when fully counterclockwise. Signals picked off the arm of resistor R50 are fed

via capacitor C25 to pin 12 of connector P1 for input to the speaker amplifier board assembly. Resistor R47 is part of the

input biasing network. The SPEAKER VOLUME control also supplies current through a second input resistor R32 to the

summing point of operational amplifier U1A whose output, representing the sum of loudspeaker and headset signals, is

fed via resistor R35 and pin 17, to the recorder circuits, if used.

(3) Regulated Amplifier. Refer to figure FO-10. The volume control module contains a regulated amplifier

consisting of U2, U4, Q1, R3 and associated components. This amplifier is identical in performance to the regulated

amplifier previously described in the paragraph on the microphone amplifier/lamp brightener module in this section.

(4) Headset Driver Amplifier. Refer to figure FO-10. The regulated signal at the output of operational amplifier U3

is fed to an

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