CHAPTER ONE: INTRODUCTION
1.1 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.
In this project work, discussions will base on design and
implementation of a two station intercom system that will result in the
instrumentation of a home to facilitate flexible one and two-way audio
conversations. The intercom circuit will consist of two intercom
stations linked to each other with a push - to - talk (PTT) switch. This
kind of circuit, generally consist of only one or two amplifiers and
generally uses loudspeakers as normal speaker and microphones (how it is
used depends on talk switch position). Depending on the circuit design,
there could be one PTT switch on one end, or separate PTTs on both
stations (as in this case).
1.2 Statement of the problem
In a business organization, shops, stores, homes etc, many people
find it difficult and stressful in relating/ delivering information
between each other within a particular building. The servant finds it
laborious going to the boss always whenever he / she has information to
deliver or wants to carry out action(s) with respect to the master's
authority. Parents within a home are even forced to walk down to the
child's room whenever need arises. As a matter of fact, reaction to
information is delayed.
Therefore, this project work is to address this issue, looking
forward to eliminating the stressful manpower involved and to facilitate
information delivery, making communication easier.
1.3 Significance of the study
The aim and objective of this project is to design and construct a
simple intercom system (mainly two communication stations) as a means to
replace man's labour and stress of walking over a given premises for
information delivery.
These station wired intercom system can be used as a door phone,
connecting from the house to the door to screen visitors to your house.
The wife, after preparing dinner, can through this system call on the
husband in his bedroom to the dinner table.
Generally, intercom system can be used for message broadcast (in case
of multi- channel intercom), as door phone, monitoring etc.
1.4 Scope of the study
The scope of this project work is limited to the design, construction
and test on a two station simple intercom system with specification
that;
i The demodulator should operate with a minimum distortion while producing an adequate output
ii. The small signal amplifier must provide an undistorted
signal into the buffer amplifier to be able to drive a speaker of 8Q. Impedance.
iii. A 9 volt d.c power supply is to be design and employed to
power the simple intercom for operation.-, at each station.
iv. The mater and the remote stations will be built individually.
v. Result' shall fully be discussed while suggestions for further study made.
1.5 Definition of some terms
In this study of simple intercom system, we shall come across terms and some of these are listed below with their meaning(s)-
DESIGN: Refers to
i A goal directed problem solving activity.
ii Relating product with situation to give satisfaction.
iii The imaginative jump from the present facts to future possibilities,
iv The conditioning factor for those parts of the product which come into contact with people.