 and one in India at the INS Kattabomman naval base.The U.S. facilities were used between 1985 and 2004 but are now decommissioned.Although the official ITU definition of extremely low frequencies is 3 Hz to 30 Hz, the wider band of frequencies of 3 Hz to 3 kHz with corresponding wavelengths from 100,000 km to 100 km.