As the key signal system guaranteeing the safety for the railway, there are two types of FSK system used now by China railway: UT signal imported from France and the homemade YP signal.

• FSK信号作为保障铁路安全运行的主要信号制式，在国内铁路上现在有两种，是法国引进的UT信号和国内自主开发的YP信号。