本文详细介绍了一种智能电话计时系统的设计与实现。该计时系统以单片机AT89C51 作为主控芯片,通过音频译码器LM567,识别出各种电话信号音和MT8870 的解码信息,以达到对用户每个主叫电话信息记录的目的;并带有合理的人机交互的显示屏和控制键盘,以便用户查询主叫信息。 关键字:AT89C51;DTMF;单片机;串行通信 Abstract:This paper introduced particularly the design and research of one kind of intelligent timing system of phone. This timing system used AT89C51 as main control single chip. By using LM567 audio encoder to identify some kinds of phone signal sounds and the encoder information of MT8870, this timing can gain its ends of recording every initiative call information of the users and sound to achieve the purpose of writing down call messages for rational human-computer interaction display and keyboard for users’ information inquiry. Key words:AT89C51,DTMF,single chip computer,serial communication