We found this circuit in the Radio Electronics Handbook magazine special edition of 1992. The circuit uses an optocoupler as an electronic potentiometer.
This circuit, which can be used as a shield, was found in General Electric documentation from the...
In figure 1 we have an application for NLAS5113, a new device from On Semiconductor...
We found this circuit in an old documentation. Transistor can be BC548 and relay according to...