Precision Time uses redundant GNSS (GPS) receiver-based time sources that are backed-up by Rubidium atomic clocks to ensure holdover accuracy. The GNSS receiver and antennas used in the Precision Time infrastructure have the capability to receive signals from multiple GNSS constellations, including GPS L1, GLONASS L1, BeiDou B1, Galileo E1, and QZSS L1. When used in concert, these time sources provide multiple levels of redundancy. The GNSS-enabled grandmaster clocks use Rubidium oscillators that can provide up to sub-microsecond accuracy when locked with the GNSS (GPS) source. Even with a loss of connectivity to the source, the service is able to maintain accuracy up to the sub-microsecond level.
