Found in an 80's Electronic Design, this circuit is based on the ICL7107 which is not an easy component to obtain today. The circuit is compatible with TTL and CMOS.
With the circuit shown it is possible to measure very low resistances, of the order of fraction of ohm,...
This circuit triggers a Sonalarme when the LED used as a sensor receives light. The circuit was...
With a touch of switch S1 the motor starts and remains so until a touch of switch S2 turns it off....