Pre selector with varicap tuning (CB9172E)

This circuit for the medium wave range was suggested by a Popular Electronics from the 90s. The double port MOSFET is an unusual component today.

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Intelligent Protection (CB17477E)
This circuit deactivates devices powered by the power grid so that when the power returns, they do...
Tone relay (CB11899E)
The trigger signal for this circuit is an audio tone. Tones up to close to 100kHz can be used. The...
Decibel Meter (CB24299E)
Found in the March 1974 Radio Electronics magazine, this circuit is designed to measure the level...