This circuit was found in the August 1994 issue of Electronics Now magazine. The 4046 is uncommon these days and the frequency range is given by C1.
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...