Continuity tester (CB7386E)

This circuit was found in a Hands-On Electronics from the 90's. The FET can be any general purpose.

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Zener Test (CB5326E)
With calibrated RV1 it is possible to find a zener diode voltage. The integrated circuit is 0 741...
PM motor speed meter (CB9348E)
This speed monitor circuit for permanent magnet motors was found in an American documentation from...
Shadow Activated Trigger 555 (CB25529E)
This fast-acting circuit uses a 555. We found it in the November 1992 Radio Electronics magazine. The...