This circuit was originally intended for reading movie soundtracks. The circuit is from 1967 and was found in an English publication. The sensor is semiconductor type.
This Schmitt trigger was found in a 1969 Ferranti documentation. Transistors may be modern...
This circuit is from the Motorola Linear Databook of 1990. The values of the components depend on the...
This circuit was found in Linear Technology Applications of 1997, using components of the time. The...