Phone Patch (CB9398E)

This circuit was found in a 1969 CQ magazine. It is intended for coupling telephones to radio amateur equipment

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Decade Counter with Nixie Tube (CB20141E)
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Crystal Radio (CB14015E)
This traditional crystal radio circuit, but which has a modern version with diode, was found in an...
Headphone amplifier (CB23888E)
This headphone amplifier using a pickup coil can be used as an extension for devices such as TVs,...