Third Order Low Pass Filter (CB25264E)

This circuit was found in the December 1990 issue of Radio Electronics magazine. It was used in a home theater sound system.

Decade Counter with Nixie Tube (CB20141E)
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
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,...