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 circuit was found in the July 1993 issue of Radio Electronics magazine. Based on an AD532, it...
This circuit is from the 1990 Motorola Linear Databook. The integrated circuit used is the LF355,...
From a 90s Popular Electronics, this circuit emits pulsating signals for different types of...