DAFTAR PUSTAKA

Agfianto Eko Putra, Belajar Mikrokontroler AT89c51/52/55 Teori dan Aplikasi, Penerbit PT. Elex Media Komputindo Jakarta.
Paulus Andi Nalwan, Teknik Antarmuka dan Pemrograman Mikrokontroler AT89C51, Penerbit PT. Elex Media Komputindo Jakarta.
Intel. MCS-51 Microcontroller Family User’s Manual, Intel Coporation, 1994.
Budhy Sutanto, Dual Tone Multiple Frequency, http://alds.stts.edu/DIGITAL/dtmf.htm 
Mackenzie S., The 8051 Microcontroller, Prentice Hall Englewood Clift, New Jersey Colombus, Ohio.
Secer Yeralen, Ashutosh Ahluwalia, Programming ad Interfacing the 8051 Microcontroller, Addison Werlwy Publising Company, 1995.