【正文】 nality and performance have been a huge increase. In general, DCS is toward more open, more standardized product in the direction of development. As the field of process automation puter control system, the traditional DCS is only a narrow concept. If only the production process that DCS automation system, which will lead to wrong conclusions, because the meaning of the puter control system has been greatly expanded, and it includes not only the DCS in the past included a variety of content, but also drill down to the each site measuring equipment, implementing agencies, upwards to the production management, all aspects of business. Traditional DCS now only refers to this part of the production process control automation, and industrial automation system concept, should be targeted to enterprisewide solution, total solution level. Only from this perspective to ask questions and solve problems, to really play the puter automation of its role. DCS has the following characteristics: (1) high reliability. DCS system to control the spread of the puter implementation, the system uses faulttolerant design of the structure, so a puter system malfunction will not cause the loss of other functions. In addition, each puter system, the tasks undertaken by relatively simple functions can be used for the need to achieve a specific structure and special puter software, so that the reliability of each puter system has also been improved. (2) open. DCS an open, standardized, modular and serial design, the system means each puter using the LAN munication, to achieve information transmission, when the need to change or expand the system functionality can be added easily connected to a puter system munication work or Remove from the work, almost does not affect the work of other puter systems. History of development of DCS DCS Distributed Control System is the abbreviation of (Distributed Control System), automation industry in the country is also known as distributed control system. It is a process by the process control level and the position of monitoring level munications work as a link to the multilevel puter systems, integrated puter (Computer), munication (Communication), display (CRT) and control (Control) and other 4C technology, The basic idea is decentralized control, centralized operations, hierarchical management, flexible configuration, easy configuration. ) Its development can be divided into three stages. Stage :19751980, during this period the technical characteristics of distributed control system as follows: 1) using microprocessorbased control unit, to achieve decentralized control, a wide variety of algorithms, through the loop control configuration independently, with selfdiagnostic function 2) The operating station with a CRT display unit and the process of separation, centralized monitoring, centralized operation 3) a more advanced munication system redundancy The second phase :19801985., Distributed control system during this period the technical features as follows: 1) increase the number of bits microprocessors, CRT display resolution to improve 2) strengthening the modular system 3) strengthen the system of information management, strengthening munication The third phase, after 1985, the third generation of distributed systems, and its technical characteristics were as follows: 1) The adoption of open systems management 2) 32bit microprocessor operating station 3) using realtime multiuser multitasking operating system Into the next decade, puter technology advances, more new technology is being applied to the DCS. PLC is a sequential logic control developed for electronic equipment, which is used instead of inflexible and cumbersome relay logic. Fieldbus Technology in entering developed very rapidly since the mid niies that some people have to predict: FCS based on field bus control system will replace the DCS as the protagonist. DCS is a Data Communication Subsystem (data munications subsystems) for short. To rail transportation industry, for example, DCS is a pure nontransparent security system, he is sent