This bistable circuit that drives a relay with a pushbutton was found in the March 1pp6 issue of Electronics Now magazine. A common bipolar with a 1k resistor at the base can be used in place of the FET.
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...