A electric insulator supporting the VLF wire antenna at the British government Rugby Radio Station, Rugby, UK in 1938. The station, completed in 1926, was a longwave VLF transatlantic wireless telegraphy station transmitting telegram traffic at a frequency of 16 kHz at output powers up to 500 kW. The antenna consisted of 16 820 ft steel masts supporting a 3 mile cage wire aerial consisting of 8 wires held apart in a circular "cage" shape by metal hoop spreaders. The end of one is visible in the picture. The insulator had to be long to withstand the 165,000 volt potential on the antenna. The wire loop around the end of the insulator is called a grading ring and reduces the potential gradient at the high voltage end of the antenna to discourage arcing.