The tuned circuit of a marine spark gap transmitter, an obsolete radio transmitter used during the wireless telegraphy. It consists of a bank of Leyden jar capacitors "(cylinders)" connected to a spiral inductor of copper strip through a quenched spark gap "(top)". It was powered with an alternating current of 10-20 kilovolts from a high voltage transformer. Alterations to image: partially removed aliasing artfacts (crosshatched lines) introduced by scanning the halftone photo using Gimp FFT filter. .