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.
Using LM3909 integrated circuits, this circuit was found in an American documentation from the...
This circuit was found in an ancient American documentation. The components of the time are not...
This circuit with low impedance output and 900k input impedance was found in the October 1993...