This circuit shows that we can implement a voltage-controlled oscillator with almost any CMOS that can be connected as an inverter. The circuit is from Radio Electronics from January 1987.
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...