Omega
A global radionavigation system that enables user with special receivers to obtain position information by measuring phase difference between precisely timed signals radiated by a network of eight transmitting stations deployed worldwide.
Note: The transmitted signals time-share transmission on frequencies of
1
0. 2,
1
1. 05,
1
1. 33, and
1
3. 6 kHz. Since the transmissions are coordinated with UTC (USNO), they also provide time reference.