Scanner squelch (CB9424E)

Found in Popular Electronics from the 90s, this circuit mutes a scanner's speaker in the absence of a voice signal, thus eliminating the hiss.

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Microcontroller Battery Regulator (CB6516E)
Found in an EDN this 80's circuit allows a microcontroller to be used to regulate a battery. The...
Heterodyne Mixer (CB4291E)
This is a typical 80's FM radio mixer circuit. The circuit was found in a documentation of the...
Operational with variable gain (CB7408E)
This operational amplifier circuit with variable gain was obtained in an 80's Electronic...