This circuit was obtained from an old American documentation, and practically any general-purpose transistor and sensitive relay can be used according to the supply voltage.
This voltage controlled oscillator, which can be used as a shield, generates signals in the 1.5...
This circuit was obtained from the 1976 Siemens integrated circuits manual. It is the circuit for...
This instrumentation circuit was found in the September 1989 Radio Electronics magazine. The...