This tone recognizer circuit that relies on R5 and C1 was found in the December 1994 issue of Electronics Now. The circuit operates on voltages from 6 to 12 V typically.
This remote-control circuit was found in Radio Electronics magazine from June 1962. It drives a...
This is the receiver for the previous circuit we found in the December 1992 Radio Electronics...
This circuit with a few watts of power was found in the April 1995 issue of Electronics Now...