Found in 1980s Electronic Engineering, this circuit uses common phototransistors as sensors. The circuit is CMOS using an integrated 4011.
This circuit is used in transceivers, enabling input selection by diode switching through polarity...
This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is...
This circuit of 1965 documentation makes use of a tunnel diode to retard a pulse without...