This circuit was found in a Radio Electronics magazine from November 1991. The circuit operates at 2.2 MHz and has a low impedance output.
Found in a 1967 Electronic Design, this transistorized circuit compresses and then expands a pulse....
This squelch is activated by its own noise, acting automatically. It is used in communications...
This is the battery-powered version of the previous circuit. The circuit is from the same Radio...