This circuit was found in an American medical documentation from 1970. The circuit rejects the 60 Hz noise pickup and generates 2.5 Hz signals. Equivalent components can be tested.
This circuit with transistors was found in an old Japanese publication, translation of an American...
This 8 W amplifier with germanium transistors was found in a Japanese documentation from 1967. The...
This circuit of the 80's makes use of components of the time. The circuit is from an American...