Techniques used for international time link

The International Atomic Time Scale (TAI) is a result of a cooperation of time-keeping labs all over the world. Time link network all over the world is used to compare the local time scales UTC (k) and Coordinated Universal time UTC. The time link data results are the base of computation of International Atomic Time Scale TAI. The long-distance time transfer technology and its development are introduced, and the status of time link between National Time Service Centre (NTSC) and TAI are presented in this paper.