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 Analog Devices documentation from the 90s. The circuit is based on a...
This circuit turns off a load after an interval of 8 to 80 seconds adjusted on the potentiometer. The...
Found elsewhere in this section, this circuit is from the April 1971 Radio Electronics magazine. Note...