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 was obtained in a 1969 documentation. The circuit modulates both the emitter current and...
This source can supply currents up to 5 A and the transistors admit equivalents such as TIP32. The...
This circuit was obtained from an English magazine from 1980, but as it uses components that can...