【正文】 the distance between trains. But it can’t work effectively because of the ATC technology limit. In this background DATC (data decentralized ATC) based on ADS (autonomous and decentralized system) developed as the level 2 system. In DATC system every train is allowed to calculate its own speed. JR East developed a kind of Shinkansen DATC, in which data munication was used. The DATC is officially called DSATC. The system is used on KeihinTohoku line called DATC, while in Shinkansen called DSATC. In the ATC system the speed signal is in the drivers cab, which received permitted speed information from the ground equipment continuously. ATC s central logic system transmits ATC signals to track circuit. ATC signals are about speed information, while they are used as train detection signals. The logic device can determine the section on which a train is present by monitoring the level of received ATC signal power because the wheels of the train short the track circuits. To set the rack circuit boundary and speed pattern is to sustain train s headway, which is necessary for train traffic control. In the ATC system the central logic system undertakes the most train interval control. The onboard system controls the braking system according to the instructions from the central logic system. Distance between trains is an important concept in railway transportation control. In this control method the system recognizes the distance between two consecutive trains firstly. Then the system controls their speed to insure a safe distance. In order to realize this distance control, various new functions are required, such as positioning exactly, high speed munication between trains and ground devices. The major difference between DATC and traditional ATC lies on that DATC is an intelligent onboard system. Every train calculates its appropriate permitted speed according to the stop position information from the ATC central logic system. Administer and Communication Technology Feature There is one point to stop one train before it crashes the preceding train. That is just to control critical stop distance. And the key information is the exact train position and where the train should stop. We know the ATC service purpose so that the basic functions of new ATC are clear. In another word equipment on the ground only transmits the train stop information, and then the train itself confirms its position and calculates the distance between it and the stop position. After that the train takes the radian and gradient into account and brakes at the proper moment. Ideal distance control model consists of trains which know each others positions. The model realized because of wireless munication technology development. In railway an area is divided into several control areas, in which ground devices and radio base stations are set up. Ground devices in every control area have many functions, such as train positioning, distance control, switching control, level crossing control and security for maintenance. Radio base stations and onboard equipment exchange information. As the appropriate interval between stations is determined according to the service area covered by radio transmissions, every base station is connected with corresponding ground control devices. The onboard puter controls brakes according to the control information from the ground devices, while it sends out the train position information to the ground equipment through onboard mobile radio base station. The first step of the control procedure is to determine the accurate train position as measured by the onboard puter. When a train enters or gets out of the boundary of a section, its original position will be recorded. Then onboard puters detect the trains speed and deal with the speed information. So the train s position track is obtained. However, when a train passes a position device on the ground, its position information will be corrected. The position detected by the system is structured into the identification numbers of the ground controller in the relevant control area, the virtual blocks into which the control area is divided, and the position within the relevant track block, and these data are processed both by the wayside and onboard puter. According to the transmitting distance restricts of radio signals, generally two base stations are constructed three miles apart. Four different frequencies are used alternately to prevent two neighbor base stations signals from interfering. For onboard system operation the practically used frequency is the most proper one of all ground radio base station in every area. Every base station must connect with trains passing it. Generally we presume that the base station municates each train in onesecond cycle. Accordingly, onesecond is divided into several time slots. Because there will be mistakes in munication, space difference system and ReedSolomon code are adopted. ReedSolomon code can correct early errors. ATACS is based on ADS (Autonomous Decentralized System) technology. In ATACS system ground devices are decentralized and connected by a work. According to the information from ground equipment the permitted speed is generated. Every trains onboard equipment can control the braking system automatically. Ground system is posed of central control system and train control system. The system is provided to devices autonomously. The advantage is that it reduces disable devices influence to whole system. What s more, it makes it possible to set up a system step by step. If one base station is out of work, an adjacent base station takes charge of its work. So the whole system can go on working. Conclusion The results of the research shows that new train control systems will be developed by