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 a 1976 Motorola CMOS manual. It can be implemented with modern Darlingtons like...
The circuit presented is from a 1972 RCA technical documentation. The integrated circuit consists of a...
We found this transmitter circuit for different frequency ranges in a 1992 documentation. The...