摘  要：随着科技水平的进步，人们生活水平的提高，电话通讯作为信息传递最便捷的工具之一已经基本的普及到了每一个家庭。而随着生活节奏的加快，白天人们都在外面工作，家里经常会只留下老人和小孩。这样如果发生突发情况，就不能及时的报警。

　　　本文主要介绍了一种以单片机STC89C52RC和DTMF编码集成电路MT8888CE为核心，基于单片机控制的电话自动拨号呼救系统。平时系统处于等待状态，在经按键触发后，调用存储在单片机里的电话号码，并由单片机控制MT8888CE拨号，实现自动呼救功能。单片语音录放集成电路ISD1420提供系统语音呼救输出。本系统可以并联在任何一部普通电话上，可满足特殊群体在遇到非常情况下的紧急求助。

关键词： 电话呼救；DTFM编码；双音多频；语音录放

Abstract:With the progress of scientific and technological level, the improvement of living standards, one of the telephone communications as information transfer is the most convenient tool is the basic universal to every family. With the quickening pace of life, during the day people are working outside, at home, often leaving only the elderly and children. The event of emergency situations, timely alarm.

　　　This paper mainly introduces a system about MT8888CE, which is for DTMF signal coding and is based on STC89SC2RC. Base on the brief of CPU’s controlling the telephone to automated ring system. And the whole circuit is in the status of awaiting opportunity. Once the key-press is touched off, the CPU will immediately go to the software to make the CMOS chip of MT8888CE for DTMF signal coding ring the correspond number which has already been input in the CPU. And then the ISD1420 output the voice to notice the helping department. The system can be parallel connected with ordinary telephone, and could meet the needs of particular people in emergency. Have realized the request designed basically through the experiment. 

Key Words: Telephone calling；DTFM code；DTFM；Voice recording and playback