０　引言水灾、火灾等险情，如能及时报警，从而采取措施，就能够最大限度减少损失．随着科学技术的迅速发展，人们报警的手段也日新月异，尤其是电话技术和程控交换技术的成熟，保证我们方便地以高速度和高可靠性进行报警．但有一些险情，尤其是火灾，往往无法预料，结果造成? 0 Introduction Floods, fires and other dangerous situations, if the alarm can be promptly taken to take measures to minimize losses. With the rapid development of science and technology, the means of alerting people are also changing rapidly. In particular, the maturity of telephony and program-controlled switching technologies ensures that we can easily alarm with high speed and high reliability. However, some dangerous situations, especially fires, are often unpredictable and the result is that?