JJY is the call sign of a low frequency time signal radio station located in Japan. The station broadcasts from two sites, one on Mount Otakadoya, near Fukushima, and the other on Mount Hagane, located on Kyushu Island. JJY is operated by the National Institute of Information and Communications Technology (NICT), an independent administrative institution affiliated with the Ministry of Internal Affairs and Communications of the Japanese government. Transmission sites The Mount Otakadoya site () is located at an elevation of 790 meters (2,590 ft) in Fukushima Prefecture. It broadcasts a 50 kW signal (13 kW ERP) on 40 kHz from an umbrella top-loading antenna situated 250 meters (820 ft) above the ground. In March 2011, it was powered down and evacuated due to its proximity to the Fukushima Daiichi nuclear disaster. It resumed broadcasting on April 21, unattended by staff. It went off air again temporarily on April 25 due to lightning, but has ever since been on air. The Mount Hagane site () is located at an elevation of 900 meters (2,950 ft) in Saga Prefecture. It broadcasts a 50 kW signal (23 kW ERP) on 60 kHz to avoid interfering with the Otakadoya site as their signals overlap. The antenna for the Hagane site is also an umbrella top loading antenna and is situated 200 meters (650 ft) above the ground. This site does not have a redundant 40 kHz transmitter, so cannot act as a fallback for the Mount Otakadoya site. Time standards Both carrier signals contain an identical pulse-width modulated time code and are transmitted 24 hours a day. Low frequency (LF) transmissions are used to enhance accuracy and reduce the possibility of atmospheric interference. The calculated accuracy of JJY's signal is 1×10−11. Japan Standard Time is set by a caesium atomic clock in Tokyo. This information is sent to the transmitter stations and is used to set a caesium atomic clock at each station. These clocks are housed in an environmentally controlled and electromagnetically shielded room to prevent outside interference with the clocks. The time code format is very similar to that of WWVB in the United States but technically is a variant of IRIG. Similarly to WWVB or MSF the signal of JJY is used to synchronize consumer radio-controlled clocks sold throughout Japan. Transmission systems Each station has an identical setup of equipment. A dual set of transmitters, a primary and a backup,