Raystor is a component of the 1960s Raytheon. It consists of a light coupler that allows you to use the circuit as a DC control for signals as shown.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...