This circuit was found in the August 1971 Radio Electronics magazine. The SCR admits equivalents and instead of the buzzer a sensitive relay can be used.
This Nixie pipe circuit was found in 1965 documentation. Note the high supply voltage. Appropriate...
This circuit is from a 1976 publication, but it can be assembled with modern components. For the...
Found in Popular Electronics from the 90's, this circuit consists of an audio oscillator for Morse...