We found this circuit in a Radio Electronics from December 1963. The circuit combines valves and transistors and has a high input resistance. The circuit is powered by two batteries.
The diagram, obtained in an old European documentation, shows the ways to trigger and to shut down...
In the figure we have a three-phase AC motor control for voltages up to 600 V or 1200 V depending on...
This shield circuit can serve as a basis for a digital mixer or simply for a switch without noise...