This circuit was found in the May 1959 Radio Electronics magazine. Its purpose is to provide bias voltages for circuits under test. The circuit is isolated from the power grid.
The circuit in the figure is based on an LM101A; diodes can be replaced with equivalents. The...
This circuit, with magnetic sensor, uses an operational amplifier of the time. The circuit is from...
Found in a 90s Popular Electronics, this circuit checks if a remote-control transmitter is...