We found this circuit in a 1966 US documentation. It simulates a variable capacitor that can vary capacitance from 1,000 to 1. Transistors are general purpose types.
This Schmitt trigger was found in old documentation. The transistors can be of the general-purpose type like...
This circuit can be used with previous transmitters to decode a signal transmitted via power grid....
This circuit was suggested by General Electric in a 1965 documentation. The circuit can be...