Loran is an acronym for long range navigation. It is an electronic system of land-based transmitters broadcasting low frequency pulsed signals that enable ships and aircraft to determine their position. A system that used this concept was first proposed in the 1930s and implemented as the British Gee system early in the Second World War. The Gee system used master and slave transmitters sited approximately 100 miles apart and used frequencies between 30 and 80 MHz. The use of frequencies in the VHF band constrained the system to ‘line-of-sight’ distance for coverage but this was not a problem at the time since the system was designed to aid bomber navigation on raids over Germany.