This circuit from a Popular Electronics from the 90s uses a common optocoupler and a general-purpose transistor to control a sensitive relay that can be from 6 to 12 V.
This circuit is from the 1997 LinearTechnology Applications, operating with input voltages from 3 to 12...
We found this circuit in the April 1992 issue of Radio Electronics magazine. The circuit uses an...
This circuit is from an old documentation. Integrated circuit 723 is not common today. The power...