Simple continuity tester (CB7955E)

This very simple continuity tester uses a small 1.5 V lamp (type used in flashlights). Can be modified to use LEDs, powered by 3 V.

Display drive 4033 (CB7554E)
We found in this American documentation this circuit for activating common cathode displays. In it we...
Simple High Pass Filter (CB25711E)
This circuit eliminates mains noise from turntables or other audio sources. The circuit is from an...
Isolated voltage sensor (CB8900E)
This shield circuit with an optical coupler was found in an 90s EDN. The circuit can be used with...