Designing And Research Of Call System For Community Based On PSTN

With the continuously raising of the living level of people, the safety service for family has being emphasized by the people. Because son and daughter has to go to work, a lot of old men (especially ill men) can't get the good care, they can't get rescue in time while appearing the emergency, this is a great safety loophole. Therefore, people expect management center can handle emergency in time through an emergency call system. With the telephone equipments popularized, it is very easy that the realization of emergency call by use of PSTN (Public Switch Telephone Network). Now, this paper will introduce a kind of emergency call system for community based on PSTN. This will bring great help for the improvement of living environment and the realization of building automation.According to the customer' s need and the market research results, the main function that this system must carry out is: When the people meet the emergency to need to ask for help, he can make a help phone call to the help center through the urgent key on the help terminal. After telephone connected, the both parties can converse. This function make the help center know the spot circumstance, in addition, the help customer can also know asking for help whether succeed through conversation. The help center established a customer database, when a help phone is sent to the help center, we decode the customer' s telephone number, then, the decoding result is input into computer, at last, search the customer database and show the search result (the customer information) on a piece of LED screen. When the help center' s telephone is busy, the help terminal can dial again automatically until the telephone connected. The function can increase the system's reliability.This paper is divided into six chapters. Chapter one introduces the need and development general situation of community help system, and givea total design project of this system. Chapter two mainly elaborate that the basic principle of DTMF (Dual Tone Multiple Frequency) and the hardware design of the help terminal. Chapter three introduces the software design of the help terminal, include the program design thought, program flow chart, the basic principle of I~2C bus and the general software package for imitation I~2C bus. Chapter four is the design and realization of the information show system, detailed elaborate that the principle of LED display, the show and type matrix of Chinese character, the protocol of serial communication and the design of the hardware electric circuit. Chapter five is a software design for help center, include the need analysis of software, the establishment of customer's database, the design of program's interface and the communication program between up computer and LED screen. Chapter six is a summary, pointing out the work this paper do and existent shortage.The emergency call system for community this paper researched has already become product through debugging and modification again and again. But for the whole building automation field, many works are treat in the further research.