William Du Bois Duddell connects a resonant circuit (capacitor and inductance) in parallel with a conventional direct-current electric arc, discovering that the arc emits spontaneous audio-frequency oscillations (a musical whistle, hence 'singing arc'). He patents the system in Britain (patent 21,629 of 1900) and notes it could be applied to wireless telegraphy, but its oscillations do not exceed the audible range (below 10 kHz), insufficient to act as a radio wave.