Light-operated relay (CB20700E)

Found in a documentation from the 70s, this circuit can be implemented today with ease. The relay is of the alternating current type.

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Transistor testing center (CB23768E)
We found this test circuit in a March 1967 Radio Electronics. The circuit uses a zener-regulated supply and...
Standing Wave Meter (CB16898E)
We found this circuit in a 1995 publication. It applies to transceivers in the citizen's range (11...
Digital sinusoidal generator (CB24473E)
The figure shows how to associate flip-flops in a shift register to obtain a lower frequency...