We found this voltmeter in a 1977 Radio Shack documentation. The integrated circuit can be the LM339 and the trigger points of the comparators are determined by the resistors. In this circuit, the trip occurs at approximately 1 V intervals.

We found this voltmeter in a 1977 Radio Shack documentation. The integrated circuit can be the LM339 and the trigger points of the comparators are determined by the resistors. In this circuit, the trip occurs at approximately 1 V intervals.