本文詳細介紹了一種智能電話計時系統的設計與實現。該計時系統以單片機AT89C51
作為主控芯片，通過音頻譯碼器LM567，識別出各種電話信號音和MT8870 的解碼信息，以達到對用戶每個主叫電話信息記錄的目的；并帶有合理的人機交互的顯示屏和控制鍵盤，以便用戶查詢主叫信息。
關鍵字：AT89C51；DTMF；單片機；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