This simple circuit was found in a Japanese magazine in 1967. The circuit is listening on a headset and the coil is 50 + 50 turns of wire 28 or thinner on a ferrite rod.
We found this circuit in an American publication from the 1990s. The triac must be equipped with a heat...
This TTL circuit uses LED indicators and must be powered by a voltage of 5 V. The capacitor...
This circuit uses an integrated CMOS having the frequency determined by the resistors and...