Found in an old publication, this is a transmitter with a spark coil. The high frequency oscillations of the high voltage spark generate the signal thrown at the antenna.
Varactor diodes are our varicaps of today. This circuit for switching signals in an RF circuit was found...
This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is...
This circuit digitally counts input pulses. The circuit from a November 1970 Radio Electronics uses...