"In a major matter, no details are small." French Proverb

Design and Implementing a 1-to-4 PBX System Using a Microcontroller

• The final project by Behdad Hosseini at University of Isfahan, Sep 2002-May 2003.

What is it?

    This is the web site of the project in partial fulfillment of the requirement for the degree of Bachelor of Science in Computer Engineering, Hardware major, Engineering Faculty, University of Isfahan, Iran, by Behdad Hosseini, Tehran, 2002-2003. The course name of the project is "Final Project".  I presented it at May 20, 2003 and got 19.75 from 20.

    This page contains the abstract, acknowledgements and links to project files and other web sites for more information. Attention: These documents are distributed just for educational purposes, therefore consider the rights, please.

Photo of the project

Abstract (abstract.txt)

    Telephone centers or more precisely, branch exchange systems, are electrical and electronical systems that are responsible for establishing telephony communications. Their behavior can be explained by making conversations between connected phones. Private Branch eXchanges (PBXs) are some kind of such systems that are mainly used in companies, organizations and other private complexes.

    In this project, I've designed and implemented a PBX system that is capable of switching 4 phones (lines) and an external connection (trunk). A microcontroller from MCS-51^TM family is used for handling and controlling the whole system. The switching unit is realized via 3 analog conversation circuits (one for each conversation connection). The hardware is implemented on 8 breadboards and the software is in the MCS-51^TM assembly language.

Acknowledgement (a part of notes.txt)

    I would appreciate assistance of my friends and especially my family in completing the project: First my father, because of his wonderful help and knowledge as I never blocked by even big problems. Second my mother; She makes home a comfortable place for live and research and every possible creative activity that can be imagined, my sister for her help in montage of some board with a lot of patience, my classmates in Isfahan especially the ones in room #105 of the Mofateh resident hall for their support: Meysam MirAlipour, Abbas Nikabadi, Amin Rezaei and especially Mojtaba Jafari for his assistance in editing my thesis by Ms Word 2000, also Mohammad Abareghi for letting me use of his Computer while I were in Isfahan (that was a major favor), and my good friends, Hossein Yarahmadi and Zahra Haghshenas, for their support in all situations, and at last but not least, Mahmoud Arab and Rouhollah Bigdeli -one of the smartest guys I've ever met- for providing me the necessary documents and books as the references of my thesis. I also like to acknowledge everybody that I've forgotten to list above. 

    And there is something that really bothers me. That's I didn't use even a little piece of wire from labs of University of Isfahan; not because of I didn't want but because of they didn't want (at least that's my thought). Anyway I didn't use and I'm really happy of that (but thinking of their behavior still bothers me). I got 14 breadboards (!) form Sharif University of Technology (www.sharif.edu) and other requirements from my father. It's appropriate to thank the staff at Sharif University of Technology for their support and trust.

Files of the Project

Web Links

• Intel 87C51/80C51BH/80C31BH Datasheet
• Intel 8XC52/54/58 Datasheet
• Intel MCS51 Microcontroller Family User's Manual
• 8051 Cross Assembler User's Manual
• Atmel AT89C52 Datasheet
• Sharif University of thechnology

This web page is last updated at 9 July 2003, adaptod for the site at 10 Jan 2008