Phase-locked loop with redundant reference input

Abstract From the Canadian patent

A phase-locked loop with redundant reference input signals comprises a means, receiving the loop feedback signal, each of the reference input signals and a reference select signal, for comparing each reference input signal to the loop feedback signal to generate corresponding phase correction signals. In response to the reference select signal one of the, phase correction signals is selected for supply as a loop correction signal. Phase and frequency detectors are included, each detector receiving a corresponding reference input signal and connected to receive the loop feedback signal for generating a phase correction signal indicating the phase and frequency difference between the …