Abstract: A securing interface apparatus to be inserted between a GNSS antenna and a first, unsecured, GNSS receiver fed by the antenna, for providing immunity against spoofing or jamming or interrupting of the timing provided by the first unsecured GNSS receiver.

Abstract: An atomic frequency standard system includes two atomic standard devices, a comparison circuit and a correction circuit. The first device operates continuously, while the second device is operated only periodically. As the second device is only periodically operated, it experiences little frequency drift due to aging effects. When operated, the second device is stabilized, and then frequency compared to the first device by means of the comparison circuit. The correction circuit is then used to recalibrate frequency of the first device with the stabilized frequency of the second device.