电子技术的发展使自动电话的结构发生着日新月异的变化,现今家用电话机也逐步用按键式取代机械拨号式。目前我国许多按键式电话机发出的拨号信号仍与机械拨号式相同,是脉冲信号,故两种电话机可以直接通换。随着科技的发展,出现了双音多频(DualTone Multiple Frequency DTMF)按键电话,此种电话机在揿动某一号码时发出相应的双音多频信号,使拨号速度比脉冲拨号信号增加十倍左右。目前, With the development of electronic technology, the structure of automatic telephone is undergoing rapid changes. Nowadays, home-use telephones have gradually replaced mechanical dialing with pushbuttons. At present, many dial-up telephones in our country still have the same dialing signal as the mechanical dialing type and are pulse signals, so the two types of telephones can be directly switched. With the development of science and technology, DualTone Multiple Frequency (DTMF) push-button telephones have appeared. Such telephones send corresponding dual-tone multi-frequency signals when a certain number is activated, increasing the dialing speed by ten times than the pulse dialing signal Times or so. Currently,