This polarity inverter circuit for voltages down to about -12 V was found in the December 1992 issue of Radio Electronics magazine. The current is a few mA.
This simple earphone receiver was sold in the 1960s in Japan. The circuit uses a single germanium...
This circuit was found in a 1967 Philips documentation. The circuit fires when light stops hitting the...
This beat frequency oscillator or BFO was found in an American 1980s documentation. The circuit is...