Synchron timing of signals in spaced transmitters and in a receiver for a phase comparison navigation system using time sequential transmissions

Claim 1

Sychronizing means for a phase comparison radio navigation system having a prime and one or more secondary spaced transmitting stations radiating phase-locked signals in a time-shared sequence, the prime station also radiating a timing identification signal, and one or more receivers for comparing the phase of the signals; which synchronizing means comprise, at the prime station, a signal source of a frequency related to the radiated frequency, digital counting means for deriving timing signals by counting signals from said signal source and means controlling the timing of the prime station transmissions in response to the output of the counter and wherein, in a receiver, there are provided means for receiving the radiated signals, means for deriving, from the received signals of said radiated frequency, a repetitive pulse counter input signal of a frequency related thereto, and a counter arranged for counting pulses from said counter input signal to derive a timing cycle corresponding to that at the prime station, and wherein the transmissions from said prime station include a timing identification signal and wherein, at the receiver, means are provided for detecting said timing identification signal and for applying the detected signal as a synchronizing signal to the counter to synchronize the counter timing at the receiver with the timing of the counting means at the prime station.