This circuit takes advantage of the hysteresis of a relay to provide a latching effect. The circuit acts as a trigger and the components must be according to the used relay.
This low power circuit for the FM band was found in a spy book from the 90s. The tunnel diode is...
This circuit was found in an old Motorola documentation from the 70s, as it uses one of its...
Suggested by General Electric in a 1970 documentation, this circuit makes use of some components of...