Figure 2-18. 1 kHz oscillator circuit simplified schematic diagram.

TM 11-6625-467-34

Hz) connects to module inputs for various tests. The

does not invert the phase of the input signal; thus

low-level voltage divider output (to the meter) con-

the feedback signal present at the emitter of Q1

nects to the metering circuit for calibration pur-

reinforces the signal at the collector to sustain cir-

poses. The 150 CPS AMPL control adjusts the cir-

cuit oscillation. The L and C parts in the collector

cuit to any desired level.

circuit of Q1 are tuned to 1,000 Hz and cause the cir-

cuit to oscillate at that frequency. Capacitor C2 and

2-23. 1 kHz Oscillator

1 KC AMPL control R9 couple the output of the

oscillator from the emitter of Q2 to the base of am-

The l-kHz oscillator is composed of four transistors

plifier Q3. The 1 KC AMPL control varies the driv-

and associated circuits that produce a 1,000 Hz sine

ing signal to Q3 to provide output amplitude control.

wave at the output. Transistors Q1 and Q2 form a

Amplifier stage Q3 amplifies the 1 kHz signal and

tuned amplifier feedback circuit that oscillates at a

p r o v i d e s a low-impedance l-kHz circuit output.

frequency of 1,000 Hz. The output at the collector of

Resistors R24 and R25 form a voltage divider that

transistor Q1 is directly coupled to the base of Q2.

provides a low-amplitude output at the junction of

The emitter follower circuit of Q2 current-amplifies

the two resistors. In position 5, switch S6F connects

the Q1 collector signal and applies it back to the Q1

resistor R27 in parallel with R25 to reduce the low

emitter circuit through the feedback circuit com-

output by one-half.

posed of R16 and Cl. The emitter follower circuit

Figure 2-18. 1 kHz oscillator circuit simplified schematic diagram.

2-59