File:Telefunken ship radio room 1919.jpg

English: Radio room on passenger ship from about 1917 equipped with Telefunken Type D spark wireless telegraphy set. It has an input power of 1.5 kW, and transmits on 600 - 200 meters (500 - 1500 kHz) with an inductively-coupled quenched-gap spark transmitter and a crystal receiver. The motor-alternator and transformer under the desk transforms the ship's DC power to 8000V at 500 Hz to run the spark gap. The transformer charges the Leyden jar capacitors (right) up, which discharge through the quenched spark gap and spiral oscillation transformer, producing radio frequency oscillations, which pass through the variometer loading coil (top) to the wire antenna strung between the masts of the ship. The radio operator transmits information by tapping on the telegraph key on the desk, turning the transmitter on and off to spell out text messages in Morse code.