This circuit for controlling high power in the AC network was found in a Motorola documentation from 1968. SCRs can be modern equivalents according to the load power.
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...