This squelch circuit is placed at the input of the single receiver audio amplifier stage. Its purpose is to silence background noise. The circuit is from an 80's documentation.
USB58xx and USB59xx Devices Integrate a 2:1 Multiplexer to Support Reversible Connection of USB...
These circuits (with some changes) are parto f the sample banl of the Multisim 11. Simulated in...
When the power is on, the 1 µF capacitor charges slowly by R1 and P1 until then on trigger...