NBFM-6 SQUELCH STAGE

A 1kHz signal and also a noise signal(not shown) is sent to the base of Q1 where it is amplified coming out of the Collector as seen on the pink line. Q2 rectifies that amplified frequency to around 2-3VDC at the Emitter. Passing resistor 11, .7 VDC or 700mVDC goes to the Base of Q3 which acts as a switch, varying the voltage at Pin7 from 4 VDC to 10VDC when the squelch knob is rotated.