Computer Monitoring And Control System Based On The Public-Switched Telephone Network

According to the technical innovation requirement by ChunHai thermoelectric plant of Dalian, a remote Monitoring and Control System is designed after analyzing the request of the project. The data from CDV-12 Gas volume corrector will be transferred through the Modem and the Public-Switched Telephone Network (PSTN). Both software and hardware working have been included in this project.First, the fundamental knowledge of the communication is introduced, followed by the introduction of the Modem, one of the most important devices used in the process of communication. Then the paper focuses on the protocols of data transference.Based on the fact that it is easy to use, debug and update the code, VB is employed as the programming tool for the central computers in the Monitoring and Control System. Although VB can not realize to read from and write to the I/O serial port directly, it provides the MSComm ActiveX control to accomplish the job.Access Database is used in this system. VB employs many language commands to access the Database in order to meet the demands of reading, writing and saving the data obtained in this system. Moreover, the function of printing is achieved by using the Excel.The Single Chip Micyoco (SCM), 89C2051, is used to design an intelligent interface box to connect the Modem with the CDV-12 Gas volume corrector. MCS-51 assemble language is used to program the software of the device. When the electric power in the city is broken down, the intelligent interface box can dial the phone number of central computer automatically to send the alarm message through the communication line.Because the Monitoring and Control System is used in the plant the old working mode has been changed, the management level and work efficiency has been improved, many economic and social benefits have been obtained. As a result, personnel and material resources are saved.