摘要：Security issue of our activity and residential zone is becoming more and more important. Developing a new home alarm system based on the public telephone network is very important to the protection of life and property safety of residents and improving the rapid response capability of departments, such as public security, fire control, medical treatment. This paper proposes a solution to design and realization the system. The whole system based on microcontroller AT89C51 is divided into hardware system and software system. Hardware system consists of pyroelectric infrared sensor, alarm mainframe, dial circuit, voice circuit, telephone interface circuit, key interface circuit. And software system includes master control modules, alarm processing modules, interrupt processing modules, dial modules, voice modules and keyboard input modules. When Infrared sensor detects alarm signal such as fire, housebreaking and emergency pulses of elder, the microcontroller receives interrupt request from prober and controls telephone interface circuit to finish simulating off-hook. Using DTMF (dual-tone multi-frequency) dial circuit to realize auto dial and voice call to play prerecorded voice messages to inform the host of the house to take measures timely. The system without rewiring is particularly applicable in the decoration and inconvenient for the user. This system has been validated by experiments, and will be a fast and effective practical solution for users.
