This circuit is from a March 1978 Radio Electronics magazine article that showed how to build it. The circuit is TTL based and is powered. The components used can still be found.
The circuit presented may use any general purpose transistor. The indicator is an LED and...
The operational amplifier used in this project no longer exists, but the circuit can be adapted to...
This car battery monitor was featured in the January 1988 issue of Radio Electronics magazine. The circuit...