File:Radiosändare - Sjöhistoriska museet - O 09136.tif

English: Part of a spark radio transmitter from the early 1900s. This was the earliest type of radio transmitter, used for transmitting information by Morse code radiotelegraphy. It consists of a bank of leyden jar capacitors which store electric charge from a high voltage transformer (not shown). To the right is an inductor consisting of a coil of wire. Above the coil is a spark gap. When the transformer charges up the capacitors to a high enough voltage, a spark occurs across the spark gap, discharging the capacitors through the coil, creating radio frequency oscillating currents in the coil. The coil is attached to a suspended wire antenna, which radiates the energy in the currents as radio waves.