We find this circuit in American documentation from the 1980s. It consists of a frequency folder using a varicap. The capacitors and coils depend on the frequency of operation.
This circuit was found in the September 1996 issue of Electronics Now magazine. The sound provided has...
This circuit was found in a Hands On Electronics from the 80's. The circuit emits an audible alert...
Radio Electronics magazine published in a 90's issue this simple alarm that can use any general...