a related circuit, the "superregenerative detector", found several highly important military uses in world war ii in friend or foe identification equipment and in the top-secret proximity fuze. an example here is the miniature rk61 thyratron marketed in 1938, which was designed specifically to operate like a vacuum triode below its ignition voltage, allowing it to amplify analog signals as a self-quenching superregenerative detector in radio control receivers, and was the major technical development which led to the wartime development of radio-controlled weapons and the parallel development of radio controlled modelling as a hobby.