This article mainly introduces a telephone with caller ID recorder whose cores are single - chip computer AT89S51 and dual - tone multifrequency decoding integrated circuit MT8870, which simulates the telephone network through dailing the recoder with the telephone, displays dialed number on the LED, meanwhile writes the calling number into EEPROM and transmits it into personal computer through RS232.The system is practical and convenient to inquiry. If the user has the telephone with caller ID service, on the basis of this system, he or she can expand his telephone into telephone with caller ID through analysing the telephone with caller ID data package. The system can also expand the local area control of the household electric appliances,and can be widely used in the household electric appliances and other kinds of control equipments.
The program of this system is written in the c language,which is solidified in the AT89C51. This article shows every part hardware structure of the system and the function the system can achieve: the DTMF coding and decoding circuit completes the decoding of the multi- sounds double frequency signal and the examination of the signal; the Liquid crystal display circuit displays the current telephone number and the amount of the telephone numbers; EEPROM storage circuit stores 10 telephone records at most; RS232 serial communication circuit can transmit the calling number into the personal computer. Moreover this article displays the writing of the software interface of the personal computer. Of this system,its design is simple, cost is low, organization is flexible and augmentability is strong. After test ,this system is effective and can achieve the expected function.
Keywords：Double Audio Frequency; Telephone with Caller ID; Serial Communications; EEPROM
