This circuit was found in the June 1991 issue of Radio Electronics magazine. The circuit uses two Hall effect sensors of the time. It can be assembled using modern equivalents.
This old oscillator using germanium transistors has a high impedance headphone as inductor to...
This old fashioned amplifier can source some watts to a low impedance loudspeaker. The circuit...
This 50 Hz rejector or notch filter was found in a 1975 documentation. Other frequencies can be...