Found in English documentation from the 1990s, this circuit can employ equivalent components. The capacitor must be low leak type. The circuit can operate as a shield.
This circuit, from a 303 Circuits from the 90s, uses a telephone pickup coil as a sensor to...
This circuit was found in Delco documentation from 1965. The transistor is of the time, but any...
This circuit appears in several versions in publications of the time and can be modified by...