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 long-time circuit uses a field effect transistor, which may be the BF245, and depends on a...
The figure shows how to implement the AND function with a Norton LM3900 operational amplifier. The number of...
This circuit is from an old documentation, but it can be elaborated with ease, since the...