GPS NTP Time Servers receive time updates from up to 12 GPS satellites and also keep accurate time via internal oscillators. System devices use the GPS NTP Time Server as a time reference to maintain accurate time via NTP across the network. Wireless Clock System Transmitters also receive time updates in this manner and pass them onto any wireless clock devices within range across multiple frequencies (ISM band hopping). Clocks act as wireless network repeaters – receiving time and rebroadcasting – resulting in a wireless mesh network for synchronising time.