Time synchronization system, as its name implies, is mainly used to provide standard synchronous signals for master control equipment, automatic equipment, computer equipment and timing equipment of weak current systems and communication systems, especially to offer standard time signals for various electronic electromechanical equipments, while the primary and secondary clock system is mainly used to provide time service for people, this is the basic difference of the both, which determines that the time synchronization system requires higher precision and reliability than the primary and secondary clock system, with more complicated structure and higher technical content. 

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Time synchronization system can obtain standard time signals from GPS satellite or Compass, and transmit the information to devices (computer, protector, fault oscillograph, event sequence recording device, safety automatic device, telecontrol RTU) that require time information in automatic systems through various interfaces, thereby enabling all communication and automatic systems in the whole region to realize time synchronization.

Global positioning system comprises one group of satellites which are launched successively by United States Department of Defense in 1978. There are 24 satellites totally moving in six geocentric orbit planes, while based on time and place, the number of satellites visible in the earth varies from 4 to 11. Compass Navigation Satellite System is one regional active satellite positioning and communication system (CNSS) that was independently developed by China, and is the third mature satellite navigation system after United States GPS and Russian GLONASS. The Compass Navigation Satellite System is committed to offering high-quality positioning, navigation and time service to global users, and develops in the four principles of “Openness, Independence, Compatibility, Gradualness”. On April 10th, 2011, China successfully launched the eighth Compass Navigation Satellite into the expected transfer orbit. The space segment of Compass Satellite Navigation System under construction is composed of 5 geostationary orbit satellites and 30 non-GEO satellites for providing two types of services, i.e. open service and authorization service (it belongs to a second-generation system). The open service is to offer positioning, velocity measurement and time services for free in service areas, with positioning precision of 10m, time precision of 50 nanosecond and velocity measurement accuracy of 0.2m/sec. The authorization service is to offer safer positioning, velocity measurement, time service, and communication service and system completeness information for authorized users. It is planned that CNSS system will cover the whole Asian-Pacific region in 2012, and spread over the whole world in 2020. 

The accuracy of the primary clock can be guaranteed by receiving standard time signals from satellites. In some core departments of our country, the GPS/Compass bimodule primary clock is utilized owing to safety requirement. The primary clock can receive GPS satellite time signals, as well as automatically judge and switch to time of CNSS with the independent intellectual property rights when GPS signals lose or generate error codes. 
The time synchronization system mainly comprises a GPS/Compass satellite timing reference source, a center primary clock (primary and standby), a secondary primary clock (primary and standby), a rubidium atomic clock (hydrogen atomic clock, or caesium atomic clock), various intelligent far-end output interface cards, various interface devices, a NTP time server, system network management equipment (control and management system), various secondary clocks, a junction box, a power supply and system signal transmission cables.