THE DESIGN, CONSTRUCTION AND TEST ON A TWO STATION SIMPLE INTERCOM SYSTEM
CHAPTER ONE: INTRODUCTION
1.1Â Â Â Â INTRODUCTION / BACKGROUND
Human to human communication is an essential part of our every day activities. Advances in communication technology have enabled any-time-anywhere connection between people. There are a wide variety of devices to communicate with family, friends and workgroup members who are distributed geographically. Cellular phones are used at the working places, stores etc. to call home to be reminded of what is needed or when one will be late to  work, meeting etc.
The purpose of a communication system is to transfer information between two or more points. In general, a communications system requires three things namely; a transmitter, a propagation  medium, and a receiver. The information to  be transferred  may be  in analog  form (example, voice or audio) as in the case of this study where voice  is the  source  of information,  or  in  digital  form (computer  data,  digitalized  voice,  and   so  on).  The transmitter must have some means of superimposing this information  onto  its  output  signal   (modulation).  The modulated   transmitter   signal   must   pass   through   a propagation medium to a receiver. The propagation medium may be free space, an RF transmission line, or a fiber optic
cable. The function of the receiver is to select (filter) the desired signal, amplify and extract the information. A simplified block diagram of a typical communication system is shown on figure 1. 0 below.
Interest arises in promoting communication within a building which is difficult and stressful going from one point to another within the building in the name of delivering information. In a domestic setting, family members will be collocated within the same building, but often will be unable to be heard using a normal speaking voice. Many households utilize intercom systems to facilitate conversations between remote parts of the home, but these systems have their drawbacks. They require one or both parties to go to specific parts of the house or hold onto a handset in order to communicate. They also offer little ability to direct communication to a person, within the house when the location of the person is initially unknown.
An intercom system is therefore a private telecommunication system that allows typically two or more locations to communicate with each other like telephone does. An intercommunication system may be a simple two- station system or a multi – station system. Many productions which need co-operation of more than a few people need special intercoms that cover many users. Intercom systems used in TV and stage productions are usually headsets type intercoms connected to one line using party line arrangement. The  primary use of this type of system  is  in  lives or media productions where (for example) the video director speaks to the camera operators, or where the stage manager speaks to the stage hands and  lighting  operator,  etc.  A simple two station wired intercom system can be used as an intercom and door phone. One can use an intercom system from the house to house gate to screen visitors to the house.
