通过proteus平台搭建关于双音频电话振铃电路设计的仿真电路，通过两种不用频率实现电话铃声的效果，大学生的必备实验操作(Through the Proteus platform, the simulation circuit of the double tone telephone ringing circuit is designed. Through the two kinds of frequency without the effect of telephone ringing, the necessary experimental operation of College Students)