Clam Lake ELF Transmitter Site, Wisconsin

A military communication system site, used to transmit emergency signals to Trident submarines. The Extremely Low Frequency (ELF) transmitting system is a back-up, one-way communication method that uses large amplitude radio waves to send commands (including potentially a launch command) to nuclear-equipped submarines. The system, which went on-line in 1984, was built because ELF radio waves are not as susceptible to interference from adversarial countermeasures, or atmospheric effects (such as the Aurora Borealis), as conventional radio waves. The system consists of two transmitter sites, this one, and one on the Upper Peninsula of Michigan.