This circuit was found in the April 1971 Radio Electronics magazine. It uses common transistors and can be adapted to use an LED or audible indicator instead of a light bulb.
This control circuit for direct current motors uses a 741 and an operational one of unusual power...
This is the traditional voltage follower configuration with the 741 operational amplifier. The...
This type of configuration can be seen elsewhere in this section. This is from a 1965 General...