Found in the CQ radio amateur magazine, this circuit generates a standard 100 kHz signal. The circuit is from 1965 and can be made with modern equivalent transistors.
This is the battery-powered version of the previous circuit. The circuit is from the same Radio...
This is the modern version of the Galena radio in which the detector is a germanium diode (which can...
This circuit triggers a remote doorbell when the phone rings. The circuit is for the 110 V mains...