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 circuit is from the 1990 Motorola Linear Databook. The integrated circuit used is the LF355,...
This high impedance amplifier is from 1985 documentation by General Electronic. The amplifier with...
Based on the TCA6600 or TCA5500 this circuit was found in a 90’s European documentation. The...