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.
We found this circuit in a 1956 documentation from Sylvania. The circuit is for bench testing and...
This circuit was found in the Radio Electronics magazine of July 19666. The search coils are the...
This circuit allows only signals with frequencies below the calculated value to pass. The formulas for...