Decca Navigator System
The Decca Navigator System was a hyperbolic radio navigation system that allowed ships and aircraft to determine their position by using radio signals from a dedicated system of static radio transmitters. The system used phase comparison between pairs of low frequency signals between 70 and 129 kHz, as opposed to pulse timing systems like Gee and LORAN. This made it much easier to design receivers using 1940s electronics, and operation was simplified by giving a direct readout of Decca coordinates without the complexity of a cathode ray tube and highly skilled operator.