High-stability clock signal regenerator with a stable fixed frequency backup clock generator

A clock signal regenerator comprising a clock signal generator whose frequency is controlled by a control signal, said clock signal generator included in a control loop for synchronizing the frequency of the clock signal generated by the clock signal generator with an input signal applied to the control loop by means of a control signal derived from the frequency difference between the clock signal and the input signal, said regenerator comprising:

• an auxiliary signal generator for producing a fixed-frequency auxiliary signal, a first difference-signal producer connected to the auxiliary signal generator and connected to receive the generated clock signal to determine the frequency difference between the auxiliary signal and a signal which is proportional to the clock signal, a storage device connected to the first difference signal producer for storing the determined frequency difference, a second difference signal producer connected to the first difference signal producer and to the storage device to determine the difference between the frequency difference stored in the storage device and a signal produced by the first difference signal producer, which signal is proportional to the frequency difference between the auxiliary signal and the clock signal, and switching means for applying in the absence of a reliable input signal the signal produced by the second difference signal producer as a control signal to the controllable clock signal generator.