This circuit makes use of a stroboscopic tube, a component that no longer exists today. The circuit is from the 70's and can be adapted to use mains voltage.
This SCS counter circuit was found in a 1964 General Electric documentation. The circuit has a...
This simple 1-transistor reflex receiver was published in Radio Electronics magazine in September 1959....
Operational amplifiers used in this 80's circuit is not very common today, but the setting can be...