Found in a 90s Electronic Design, this circuit operates with Maxim components of the time. The circuit operates at 50 MHz with a 10 V x 50 mA current.
Found in a 1966’s General Electric documentation, this circuit uses a triple diode from the time....
Found in documentation from the 1990s, this circuit converts 12 V to 9 V from a car's power...
This ohmmeter can be made with a scrap milliammeter used for continuity tests or even resistance...