Found in an Analog Devices documentation from the 1990s, this circuit has a feedback resistor to compensate the gain.
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...