2) LED as a Continuity tester: The above shown circuit is LED as continuity tester. This circuit is used for checking continuity of cables, connectors and switches. When A and B terminals are shorted, ...

This simple but clever continuity tester sports two LEDs: RED LED = circuit resistance is < approx 10K, GREEN LED = circuit resistance <10Ω. It consumes approx 8mA from a 9V battery. When not ...