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 is from a Mallory 1968’s documentation. The integrated circuit is of the time and the...
This circuit generates low-frequency sinusoidal signals. The variable capacitor is dual and the...
With this circuit, a well known configuration, small speakers and even low-impedance headphones...