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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Tone detector (CB9697E)
Found in a 1980s American documentation, this circuit operates with 5 V signals requiring 55...
Modified Hartley Oscillator (CB21138E)
This circuit was found in old American documentation. Transistor is general purpose and coil rated...
Signal Converter (CB16918E)
This circuit uses a NAND port to convert rectangular signals from 50 kHz to 1 MHz into triangular...