This circuit uses an optical coupler called Raystor created by Raytheon in the 1960s. The circuit uses components from the era that can be changed. The current is low.
This circuit was found in a Popular Electronics from April 1993. It is a voltage regulator circuit...
This circuit was found in a 1967 US documentation. It shows how to build a gain control by digital...
This circuit was found in an American 1960s documentation. The circuit uses transistors of the...