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Cover page                                                                       i

Title                                                                                 ii

Certification                                                                     iii

Dedication                                                                       iv

Acknowledgement                                                            v

Table of Content                                                               vi


1.0 Introduction                                                               1

1.1 Background of Study                                                  1

1.2 Problem of Study                                                                2

1.3 Aims of Study                                                             4

1.4 Significance of Study                                                  4

1.5 Scope of Study                                                           5

1.6 Limitation of Study                                                     5

1.7 Project Outline                                                           6


2.0 Literature Review                                                       8

2.1 Uses of Intercom                                                        8

2.2 Component Description                                              9

2.2.1 AT89C52 Microcontroller                                         9

2.2.2 Crystal Oscillator                                                    19

2.2.3 Resistors                                                                 19

2.2.4 Capacitors                                                               24

2.2.5 Speakers                                                                 25

2.2.6 IC Sockets                                                               26

2.2.7 Transistor                                                               26

2.2.8 Switch (ON/OFF)                                                     27

2.2.9 Battery                                                                    27

2.2.10 MIC Condenser                                                     28

2.2.11 Pattress                                                                 28


3.0 System Design and Methodology                                30

3.1 Method of Construction                                              30

3.2 Block Diagram of a Microcontroller based eight way

Intercom System                                                        33

3.2.1 The Power Supply Unit                                            34

3.2.2 The User Input Unit                                                35

3.2.3 The Microcontroller Unit                                          36

3.2.4 The Switching Unit                                                  38

3.2.5 The Amplifier Unit                                                   38

3.3  Complete System Unit                                               39

  1. 4 Circuit Analysis and Implementation 40

3.4.1 Power Supply Unit                                                   40

3.4.2 Microcontroller Unit                                                40

3.4.3 The Amplifier Unit                                                   42

3.5 Principle of Operation                                                 43

3.6 Components Connection Analysis                              44

3.7 Implementation                                                          46

3.8 Software Development                                                46


4.0 Test Result and Discussion                                        52

4.1 Testing                                                                       52

4.2 Result                                                                        53

4.3 Discussion                                                                 54

4.4 Bill of Engineering                                                      55


5.0 Conclusion, Recommendation and Future Work         56

5.1 Conclusion                                                                 56

5.2 Recommendation                                                       56

5.3 Future work                                                               57

5.4 Problem encountered                                                  57


















An intercommunication system is the communication between two or more persons not close to one another. In this project however, an intercom system involving short distance places is designed and a constructed. This intercom involves 8 users where  8 persons could communicate with each other. It utilizes both hardware and software. The hardware aspect comprises a microcontroller (AT89s52), a latch (74373), transistors (Bc 337, TIP 42), capacitors, resistors, diode, relays, keypad, veroboard. The software was written in an assembly language. The intercom is an 8 way station type which means that a station at its own convenient time. Users can call one another’s attention by the use of the tone generator. When a button is depressed, the tone sounds and the same switch is thrown to the intercom circuit thus they communicate. This system is to be used in solving the problem of poor communication in the EEE department. It can also be extended to other offices.



















An intercom (intercommunication), talkback or door phone is a stand-alone voice communication system for use within a building or small collection of buildings, functioning independently of the public telephone network (Wikipedia, 2015). Intercoms are generally mounted permanently or otherwise in buildings as well as vehicles. Intercoms can incorporate connections to public address loudspeaker systems, walkie talkies, telephones, and to other intercom systems. Some intercom systems incorporate control to devices such as signal lights and door latches.

Intercom is a personal telecommunication device which facilitates the exchange of messages between two or more locations where standard vocal communication would be difficult or impossible due to distance or obstructions. Basic intercom systems have been in existence since about a decade into the twentieth century, if one only consider designs reliant on that rather handy invention of Alexander Bells telephone (Encyclopedia,2011). Present day intercom systems are as varied in their forms, as their uses. Uncomplicated two-way devices are employed for such functions as access control for the gates and doors of homes, shops and business. Once a visitor has announced his/her presence over the intercom, the occupant of the premises decides whether to let them in or not.

Intercom can be wired or wireless, but as regards this project, wired intercom will be designed and implemented. Intercom can run on a normal power supply as well as a special battery, depending on the manufacturer.

In the past, the installation of intercom systems required a lot of heavy wiring and expensive upkeep. Today, there is no constant maintenance needed after your intercom system has been set up. In addition, there are wireless intercom systems available now that make installation much easier. Also, intercom systems can be integrated with security systems and other systems. For example, a home and security system can be joined with your telephone line. When someone is at your door, it will alert you with a text message or phone call. If you happen to be away from home, you can receive a call to your cell phone if someone rings your bell. The home intercom system can also be integrated with your sound system to play music throughout rooms.


One major problem faced before the invention of intercom system was the problem of communication barriers. Some other problems are problem that we encounter in our day to day activities which includes:

Problem of insecurity in the home, offices, hotels etc.: This problem has to do with the fact that before the invention of intercom, one has to open the door by his/herself in order to know who is at the door. Most cases it may not be somebody who you wanted to see. There have been cases of robbery because of the fact that the occupants of the building do not have first-hand knowledge of who was at the door.

Problem of rowdy movement within a big building: This problem is mostly common in offices and hotels. People moving from one part of the building to another just to pass information.

Problem of communicating with prison inmates: This is a very big problem faced in the prison before the invention of intercom. This is because in a bid to allow the inmates discuss with their visitors, they may end up planning and taking that same visitor as a hostage just to make their way out of prison. This is the much reason that modern day prisons now have a section were multiple two-way intercom systems are mounted with a very thick transparent glass that separates the section of the visiting room, with the two units of the intercom placed on the two section of the demarcation. This technology enables the prison inmate see the visitor as well as communicates with them through the intercom.

The above listed problems are some of the numerous problems faced without intercom. The modern day intercom which now comes with various features has helped to solve and address these problems just the same way this microcontroller based two-way intercom have solved the problems as well. More lines can be added to the design. But as regards this project, it is just a eight-way design.


The aim of this project is to design:

  1. A microcontroller based eight-way intercom system with 8 users.
  2. A system with a full duplex mode of communication.
  • A portable system that is cost effective with low power consumption.


Nowadays, a lot of people are considering having home intercom systems installed in their houses. Both for the purpose of security and convenience.

This study is necessary because:

  1. Specifically, intercom provides security in the home; with a home intercom system installed, one will be able to check house visitors first by just speaking through the intercom and wait for the visitor to respond.
  2. The study is necessary because it helps provide a sense of peace and order in a big house e.g. hotels. For a house that has multiple rooms, having an intercom system installed in the house can be a very convenient way of communication. Without an intercom system, it is possible that there would be a lot of shouting happening, as well as a lot of movements back and forth between rooms.
  • This study is also important in monitoring important areas of a building.


The scope of this project covers the concept of communication in a eight way full duplex mode using a microcontroller based eight-way intercom system. It covers also the security of a building (home, offices, and so on) that is screening of visitors before granting them access into the building. The scope of this project design also covers the casing of this device. This was achieved by using a condemn intercom phone to serve as the case that house the circuit board on which all the connections of the various components were done.


The limitation of this project is nothing much, other than the fact that the system is designed only for the purpose of communication within a specific area or location. This means that the device does not perform any other function that differs from communication. Some other limitations of this project include:

  • Communication is only possible when there is a user at the two end points of the units.
  • The device cannot be used outside the intended building. This is because the device is wired (i.e. there is a wired connection between the eight unit) making it impossible to be moved around like the normal cell phone.
  • Since the device is a eight -way intercom, it means that it is restricted to only eight users.


  • Chapter one introduces the project topic, its problems, scope, limitations, aims and objectives of the project.
  • Chapter two reviews the project, including related works. It also discuss about the components used in the project.
  • Chapter three covers the research and methodology of the project. It also covers the circuit design, assembling, operation and implementation of the project.
  • Chapter four discusses about the test, result and discussion of the result obtained during the project analysis.
  • Chapter five deals with the conclusion and recommendation and future works of the project.



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