This very simple circuit uses a phototransistor and a very sensitive relay (reed type) being used over short distances with a lens system. The circuit is from a 1967 Japanese publication.
This amplifier with high input impedance was suggested by National Semiconductor in its 1994...
This circuit synthesizes the tick of a metronome with the speed controlled in RV1. The circuit is...
This circuit makes use of an unusual component which is a large surface diode that can be used to...