Found in documentation from the 1980s, this circuit uses a SG1524. It is an uncommon integrated circuit nowadays. The circuit provides a current of 20 mA with a symmetrical voltage between 15 and 18 V.
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...