This is the circuit for the HM-10ª, an instrument sold by Heathkit. The circuit is from a Radio Electronics from May 1963. The indication is by an analog instrument.
This is a typical source of the time (1989) using the well-known regulator integrated circuit 723....
This 8 A high output power amplifier uses two National Instruments LM12s. The maximum capacity of the...
Found in Popular Electronics from the 90s, this circuit turns off an appliance at the end of the...