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.
The power supply shown below is used to supply continuous voltages between 3 and 12 V to small...
We found this good power amplifier with the LM12 integrated circuit in the March 1989 issue of...
This Linear Technology circuit was found in a 1980s documentation. The circuit can swing up to a...