Spark gap transmitter of early transatlantic wireless telegraphy radio station built by Gesellshaft fur Drahtlose Telegraphie at Nauen, Germany 1907, which served as Germany's main communication channel with other nations during World War 1. The bank of narrow Leyden jar capacitors are visible in the background. On the right are tank coils that, connected to the Leyden jars, make up the tank circuit of the transmitter. The technician is working on the spark gap. The station had an input power of 35 horsepower (26 kilowatts) and radiated in the very low frequency band using a large wire umbrella antenna.