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.
Found in a 1965 Radio Shack documentation this oscillator can be used with modern general purpose...
In the figure we have the way to use a single control voltage to act on two varicaps...
Found in a 90s documentation, this switch that is also sensitive enough to operate capacitively uses...