1. DESIGN AND CONSTRUCTION OF A SIMPLE
TWO WAY INTERCOM. SYSTEM
BY
A PROJECT SUMITTED TO THE DEPARTMENT OF ELECTRICAL AND
ELECTRONIC ENGINEERING TECHNOLOGY ABIA STATE
POLYTECHNIC, ABA.
IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF
NATIONAL DIPLOMA (ND) IN ELECTICAL AND ELECTRONIC
ENGINEERING
JANUARY, 2016
CERTIFICATION

2. I certify that this project design and construction of a two way intercom system
was carried out by me, IGWE LUCKY CHIMEZIE with matriculation number
2013NDM/000137/EE in partial fulfillment for the requirement for the award of
the national diploma in electrical/electronic engineering, abia state polytechnic,
aba.
DECLARATION
I hereby declare that this project design and construction of a two way intercom
system was designed, constructed and submitted to the department of
Electrical/Electronic Engineering, Abia state polytechnic, aba. In partial fulfillment
of the requirement for the Award of national diploma.
I further declare that this work has not been submitted to this or any other
institution for the award of degree, diploma or equivalent course.

3. DEDICATION
This project work is dedicated to GOD Almighty and also to my family for their
support.

4. ACKNOWLEDGEMENT.
My profound gratitude goes to GOD Almighty for his grace upone my life.
Am indebted to my supervisor for his professional and fatherly advice in the
actualization of this project work and also my co-coordinator for his advice and
encouragement.
Special thanks to the staff of Electrical/Electronic Engineering for their academic
and moral impartations; you were all great may GOD bless you all amen.
My gratitude also goes to my family members for always being there for me,
especially to my brother for his supportand also my parents chief and Lolo.
Emmanuel igwe for their parental guidance I cannot thank you people enough but
keeping asking GOD to keep you all healthy with long life to reap the fruit of your
labour Amen.

5. ABSTRACT
Designing and implementing multiple intercom system that will work without
charges has always been a prominent field of interest among many researchers and
developers. This project presents developments and potentials of a two way
intercom system that allow two way conversations from one location to another
within a particular place such as offices, homes, workshops, warehouse. This
project writing discussed an intercom system and its component make-up,
operation applications and other relevant issues as regards to intercom system. The
basic element used in this project are tone generator, audio input source, audio
amplifier, output device and medium (cable). As both microphone (input source)
are always in operation, 1000uf capacitor was used in the power circuit to avoid
loud speaker from being picked up by the microphone enclosed in the same box,
causing a very undesired and laud.

6. TABLE OF CONTENTS
Title……………………………………………………………………….i
Certification…...………………………………………………………….ii
Dedication……………………………………………….……………….iii
Acknowledgement………………………………………………………..iv
Abstract………………………………………………….………………..v
Table of contents…………………………………………………………vi
List of figures…………………………………………………………….vii
Chapter one
1.0 INTRODUCTION
1.1Background of
study……………………………………………………………………….1
1.2 Statement of
problem……………………………………………………………………2
1.3 Objective of
study……………………………………………………………………….2
1.4 Significant of the
problem……………………………………………………………………3
1.5 scopeand limitation of study………………………………….………3
Chapter two
2Lliterature review…………………………………..……………………5

7. 2.1 Background of study………………………………………………….5
2.2 Historical
background…………………………………………………………………6
2.3 Background and mathematical techniques…………………………..…9
2.3.1 How it
works…………………………………………………………………….…9
2.3.2 Calculation…………………………………………………………..10
CHAPTER THREE
3 DESIGN METHODOLOGY AND IMPLEMENTATION………………12
3.1 COMPONENT
IMPLEMENTATION………………………………………………………12
3.2 COMPONENT IDENTIFICATION AND THEIR
VALUES…………………………………………………………………….14
3.3 PREPARING THE VERO
BOARD………………………………………………………………………15
3.4.1 INSPECTING THE VERO
BOARD………………………………………………………………………15
3.4.2 SOLDERING…………………………………………………………..16
3.5 TESTING THE CIRCUIT………………………………………………..17
3.6 PRINCIPLE OF
OPERATION…………………………………………………………………17
3.6.1 POWER SUPPLY :( BATTERY)………………………………………18
3.6.2 INPUT SOURCE:(MICROPHONE)…………………………………...19
3.6.3 OUTPUT DEVICE: (SPEAKER)………………………………………19
3.6.4 MEDIUM: (FLEXIBLE WIRE)………………………………………..19

8. CHAPTER FOUR
4 DATA PRESENTATIONAND
ANALYSIS…………………………………………………………………...21
4.1 TONE
GENERATOR………………………………………………………………..23
4.4 CALCULATION…………………………………………………………25
CHAPTER FIVE
5 CONCLUSION AND RECOMMENDATION……………………………...29
5.1 CONCLUSION……………………………………………………………29
5.2 RECOMMENDATION……………………………………………………30
REFERENCES…………………………………………………………………32

9. LIST OF FIGURES
FIG 3.1 application circuit for the 555 timer…………………………………10
Fig 3.2 the block diagram……………………………………………………..13
Fig 3.3 circuit diagram of the audio amplifier………………………………...14
Fig 4.1 circuit diagram of the ringer…................................................................18
Fig 4.2 pin outs of NE555 timer IC…………………………………………....23
Fig 4.3 application circuit for the 555 timer…………………………………...24
Fig 4.4 circuit diagram of the audio amplifier…………………………………26
LIST OF TABLES
Table 4.1 current variation in resistors…………………………………………22
Table 4.2 bill of quantity and evaluation (BEME)………………………….…27

10. CHAPTER ONE
1. INTRODUCTION
An internal communication system is a system that basically transfers
information in the form of electrical signal from one spotto the other within a
confirmed location. It is also a private telecommunication system that allows
typically two or more location to communicate with each other like telephone
does. An intercom is also a personal telecommunications 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.
This project two way intercom system consist of station linked to each using
wire. It uses full duplex .modea process whereby one can transmit and receive
voice calls simultaneously which made transmission medium to be your wires
between the two nodes and typical headers on the nodes (separate speaker and
microphone, good isolation from sound coming from speaker to the mic
element).
1.1 BACKGROUND OF THE STUDY
Technology now has made it possible for various instrument or device to be
designed and constructed in other to make human life more profitable and
enjoyable. These days, a lot of devices are built based on electrical approach.
One of these devices is known as an intercom system.
Perhaps one needs an internal communication. May be may be one want to be
able to communicate with his home from his office or garage. Or in a case one
is upstairs in a bedroomdoing his or her schoolwork, and wants to know when
dinner will be ready. May be the personis too weak to get up and shout down
the stairs to find out if so, then this simple intercom will help him or her to get
the information he or she needs. It works without6 charges on like the
telephones.

11. Two way wired intercom systems enables sound or speechto be transmitted in
two directions, therefore enabling a conversation. Intercoms are generally
compared of fixed microphone/speaker units which connect to a central control
panel. In general, a communication 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 sourceof information, or in digital form (computer
data, digitalized form and so on).
1.2 STATEMENT OF PROBLEM
In a business organization, shops, stores 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 respectto the master’s authority.
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. The intercom system forming the basic
of this study and designed to serve the HOD’s office and the secretary’s office
for internal communication.
1.3 PURPOSE
(1) The main objective of this project is to constructa two way wired intercom
that will help two persons or more to communicate with each other within a
particular domain, like offices homes, warehouse e.t.c.
(2) To build a telephone that will transmit signal via a medium at no cost.
(3) To immensely help the engineering students understand the technology
behind two way simple intercom and its practical development.

12. 1.4 SIGNIFICANT OF THE STUDY
The design and construction of two way intercom system will help students or
individual to understand the basic knowledge of intercommunication industries,
also it’s 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 doorphone, connecting from the house to the doorto screen visitors
to the house. The wife, after preparing dinner, can through this system call on
the husband in his bedroomto the dinner table. Generally, intercom system can
be used for message broadcast(in case of multi-channel intercom), as door
phone, monitoring etc.
1.5 SCOPEOF PROJECT
The scopeofthis project work design of simple two way intercom system is to
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 8 ohms 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. Result shall fully be discussed while suggestions for further study made.

13. CHAPTER TWO
LITERATURE REVIEW
2.0 HISTORY
This chapter will emphasize on the research carried; intricate on ways in
which this assist the design at end.
The audio amplifier which was converted into two way intercom was
invented in 1959 by lee de forest when he invented the vacuum tube. The
triode was a three terminal device with a control grid that can modulate the
flow of electrons from the filament to the plate. The triode vacuum amplifier
was used to make the first AM radio.
Early audio amplifiers were based on vacuum tubes (also known as valves),
and some of these achieved notably high quality (i.e the Williamson
amplifier of 1747-9). Most modern audio amplifiers are based on solid state
devices (transistors such as BJTs and MOSFETs), but there are still some
who prefer tube-based amplifiers, due to a perceived ‘warmer’ valve sound.
Audio amplifiers based on transistors became practical with the wide
availability of inexpensive transistors in the late 1960s. Key design
parameters for audio amplifiers are frequency response, gain, noise, and
distortion.
These are interdependent; increasing gain often leads to undesirable
increases in noise and distortion. While negative feedback actually reduces
the gain, it also reduces distortion. Most audio amplifiers are linear
amplifiers operating in class AB (ONOH G.N 2005). Historically, the
majority of commercial audio preamplifiers made had complex filter circuits
for equalization and tone adjustment, due to the far from ideal quality of
recordings, playback technology and speakers of the day. Using today’s high
quality (often digital) source material, speakers,etc, such filter circuits are
usually not needed. Audiophiles generally agree that filter circuits are to be
avoided wherever possible today’s audiophile amplifiers do not have tone
controls or filters.

14. Since modern digital devices, including CD and DVD players, radio
receivers and tape decks already provide a “flat” signal at line level, the
preamp. Is not needed other than as volume control. One alternative to a
separate preamp is to simply use passive volume and switching controls,
sometimes integrated into a power amp. To form an “integrated” amplifier.
For some years following the introduction of solid state amplifiers, their
perceived sound did not have the excellent audio quality of the best valve
amplifiers. This led audiophiles to believe that valve sound had an intrinsic
quality due to the vacuum tube technology itself. In 1972, matti otala
demonstrated the origin of a previously unobserved form of distortion:
transitory intermodulation distortion (TIM),also calledslew rate distortion .
TIM distortion was found to occurduring very rapid increases in amplifier
output voltage. TIM did not appear at steady state sine tone measurements,
helping to hide it from design engineers prior to 1972. Problems with TIM
distortion stem from reduced open loop frequency responseof solid state
amplifiers. Further works of otala and other authors found the solution for
TIM distortion, including increasing slew rate, decreasing preamp frequency
bandwidth, and the insertion of a lag compensation circuit in the input stage
of the amplifier. In high quality modern amplifiers the open loop responseis
at least 20KHz,canceling TIM distortion . however, TIM distortion is still
present in most low price home quality amplifiers. The next step in advanced
design was the Baxandell Theorem, created by peter Baxandell in England.
This theorem introduced the conceptof comparing the ratio between the
input distortion and the output of an audio amplifier. This new idea helped
audio design engineers to better evaluate the distortion processeswithin an
audio amplifier. Important applications include public address systems,
theoriticaland concert sound reinforcement, and domestic sound systems.
The sound card in a personal system contains several audio amplifiers
(depending on number of channels), as does every stereo or home-theatre
system.

15. 2.1 BACKGROUND AND MATHEMATICAL THEORY OF THE WORK
The intercom system works in the principles of modulation demodulation
(modem). This means that outside the power section of the system, there are
basically two segments in the gadget viz. modulation segment and the
demodulation segment (V,K Mehta,1998). Other sub parts include the input and
output transducers, the transmission channel, the audio amplifier, the bias circuit,
the trimmer circuit and the volume control.
The element microphone receive the signal which is the human voice and its
frequency falls within a limited band of 300HZ to 3.4 KHz approximately and
convert it into audio frequency voltage signal which is very small and has to be
amplified. This design uses transistor Q1 which is 1800 phase shifted as
microphone amplifier and the collector and its in-phase output taken at the emitter
and mixed mixed by C3, C4, R7 and R8 network. R7 is timed until the two incoming
signals almost cancel out. In this way, the loud speaker will reproducea very faint
copyof the signals picked-up the microphone. At the same time, as both collectors
of the two interconnects are tried together, the 1800 phased-shifted signal will pass
to the audio amplifier of the second unit will be attenuation so it will be loudly
reproduced by its loud speaker.
The same operation will occurwhen speaking into the microphone of the second
unit. The audio power amplifier used by the circuit is TDA2003 audio power
amplifier IC which is capable of delivering about 1 wait of output power at a
supply voltage comprised in the 6-12V range.
The loud speaker in this case is the receiver of the gadget which persons he work
of converting the electrical energy into the original sound energy.
2.1.1 CALCULATION
Using Ohm’s law to determine the current and power in a circuit using the
8Ω speaker.

16. I =
𝑉
𝑅
Maximum output voltage = 1
2⁄ (supply Voltage of the IC) of any amplifier circuit.
All the semiconductor in this project is powered using 6 Volts battery. This implies
that:
Maximum output voltage of the audio IC = 1
2⁄ × 6 = 3𝑉
I =
𝑉
𝑅
I =
3
8
= 0.375 Amps.
=VI
3 × 0.375 𝐴𝑚𝑝𝑠 = 1.125𝑤𝑎𝑡𝑡𝑠.

17. CHAPTER THREE
CONSTRUCTION
3.0 DESIGN ,
Below are basic steps taken during the research and designing stages of this
project;
 Browsing the internet for relevant for relevant information on the project
topic
 Existing circuit diagrams sourced for
 Then studied and analysed the diagrams to arrive at our choice of dragram
which was based on simplicity, effectiveness and comprehensive
 Changes were made on the circuit to further ensure effectiveness. Some of
these changes included choice of microphone and speaker. Finally, arrived at
the block below.
1.1 component implementation
Using Ohms law to derive the component values used in the circuit by first
principle by considering resistors in series (A.J Watkins 1983).
R1 + R2 + R3 ……….Rn
Considering the 9voilt that is needed to power the circuit and semiconductor
was considered when the range of 9 volts and the maximum current is8mA.
Example, R = VI, 9 × 8 = 72KΩ, so every other componentwas chose
having tested with the voltage and current mentioned above.

18. FIG 3.1 CIRCUIT DIAGRAM
FIG 3.2 BLOCKS DIAGRAM

19. 3.4 PREPARING THE VEROBOARD
This work completed by using a veroboard to assemble the above explained
electronic components. The process described below was taken, to prepare
the veroboard.
Grab a very sharp carft knife and a ruler. On the track side of the board,
count 40 complete holes along a track, then place the ruler perpendicular to
the next hole and cut off the unwanted lines.
Now turn the board over, and repeat the operation in exactly the same place
on the componentside. Pick up the board and snap it with both hands,
keeping your fingers close to the scoremark on either side it should break
evenly, leaving you with two rectangular pieces. Now (if the board is too
wide) do the same thing again, but along the 40th track and scorethrough the
holes on that track. Do the same on the other side, then snap. If all went
well, you should now have a piece of veroboard of the correctsize- 39 tracks
by 40 holes(onuha R.U 2011).
3.4.1 INSPECTING THE TRACKS
Very occasionally, a piece of veroboard will have defects such as small
splashes of copperbridging adjacent tracks. Inspect the board carefully to
make sure there are no bridges. If you do find any fault rn your knife
between the tracks in other to cut it (onuha R.U 2011).
3.4.2 SOLDERING
Soldering is the process ofmaking a sound electrical and mechanical joint
between certain metals by joining them with a softsolder. This is low
temperature melting point alloy of lead and tin. The joint is heated to the
correct temperature by soldering irons are used. These consist of a handle
onto which is mounted the heating element. On the end of the heating
element is what is known as the “bits”, so called becauseit is the bit that
heats the joint up. Solder melts at around 190 degrees centigrade, and the bit
reaches a temperature of over 250 degrees centigrade. This temperature is
plenty hot enough to inflict a nasty burn, consequently care should be taken,

20. Good soldering is skill that is learnt by practice (T.G Francis 1988). The
most important point in soldering is that bothparts of the joint to be made
must be at the same temperature. The solder will flow evenly and make a
good electrical and mechanical point only if both parts of the joint are at an
equal high temperature. Even though it appears that there is a metal to metal
contact in a joint to be made, very often there exists a film of oxide on the
surface that insulates the two parts. For this reason it is no good applying the
soldering iron tip to one half of the joint only and expecting this to heat the
other half on the joint as well
3.5 TESTING THE CIRCUIT
After the construction, the circuit was properly analyzed and short circuit
and open were all corrected. The two circuit are the powered with a 220V ac
supply with two persons holding the handset at two ends.
One of the person dial the other by pressing the ringer switch, the recipient
at the other end picks his handset and full duplex communication took place.
The same process was repeated but this time recipient dialing the caller and
clear communication was established.
At this point, it was concluded that there was no error and the project couple
coupled and cased.
3.6 PRINCIPLE OF OPERARTION
The principal of operation of this work (Two-Way Wired Intercom) will be
properly understood by taking the analysis of the stages that make up the
entire system. Complete circuit is run on 6volts 4.5Ah battery (V.K MEHTA
1988). The battery is where all the sub circuit such as the audio amplifier
and the tone turning on the switch, all the sub circuit will be set to receive
power from the sourceas the phone handle is lifted up except the tone
generator circuit which is powered immediately so that any tone received
from UNIT 2 will be amplified to tell the user UNIT 1 that UNIT2 want to
establish conversation. Any of the users will tell the second users that he
wants to establish conservation by pressing the ringer button. This sends a

21. tone signal to the phone and conversation is successfully established when
the users must have picked up the phone.
The handle of the phone is where the microphone (mouth piece) and the ear
piece are located. Any sound or speech made by any o f the user is picked up
by the microphone as mechanical vibration and converted to electrical signal
that has a voltage frequency which its amplitude varies linearly with time
(alternating), and a frequency which is a replica of the frequency of
vibration. This electrical signal has low transistor (C1815) connected in
active region. It is then sent to the power amplifier were the final
amplification is made. The ear piece connected through a relay switch so
that it is activated and deactivated by pressing the voice out switch. On
dropping the phone, other sub circuits are deactivated leaving only the tone
generator activated. The internal battery can be charged by charged by
plugged the mains wire to socketand switching on the system.
3.6.1 INPUT SOURCE(MICROPHONE)
The input sourcecontains the transducer which converts the sound (speech)
in form of mechanical vibration to electrical signal. The electrical signal has a
voltage which its amplitude varies linearly with time. The transducer in this block
is a capacitor (condenser) microphone (Geoffrey E and Jan S 1989).
FIG 3.3
3.6.2 OUTPUT DEVICE (SPEAKER)
The basic aim of every telephony system is for one to successfully transmit or
receive voice (speech) with minimum interference. This speech being an electrical
signal which has a voltage of varying amplitude cannot be seen or understand the
content by feeling, hence there must be a device which will reproducethe
equivalent of the electrical signal being transmitted. This device is the speaker and

22. it does that by converting the electrical signal into mechanical vibration
(diaphragm moving back and forth). The speaker contains basically the diaphragm,
coil and magnet (A.K THERAJA 2003).
FIG 3.4
3.6.3 MEDIUM (FLEXIBHLE WIRE)
In every communication system, there must be a medium through which data is
being sent or received. The medium includes; air/spaces as in electromagnetic
wave, fiber optic cables as in laser beam and strands of coppercable as in electrical
signal. The medium through which the data is being transmitted in this project is
flexible wire. When a communication network is established, user 1 talks to the
microphone on his headset and user 2 hears it from the speaker on his own headset
and vice versa. I.e. the voice at one terminal is amplified and sent through the
medium to a speaker at the other terminal. Because this is a full duplex kind of
hear simultaneously.

24. CHAPTER FOUR
4.1 DATA PRESENTATION AND ANALYSIS
Using ohm’s (Ω) law to determine the current that flows through each of the
resistors in the circuit in the both sub-circuit.
Assuming different voltages passed through each of the resistor, from 12-6v.
I = V/R = ……………………………….(4.1)
I1 = 12
47,000 = 2mA ……………………...(4.2)
I2 = 11
330,00 = 3mA …………………..…..(4.3
I3 = 10
2200 = 4mA …………………..…...(4.4)
I4 = 9
220,00 = 4mA ………………….…..(4.5)
I5 = 8
100,00 = 8mA ……………………..(4.6)
I6 = 7
300,00 = 2mA ……………………..(4.7)
I7 = 6
330,00 = ImA ……………………..(4.8)
Total current passing through the resistors.
I1 + I 2 +I3+ I4 +I5 +16 = (……………………(4.9)
2 + 3 + 4 + 4 + 8 +2 + 1= 24mA

25. 4.2 CURRENT VARIATIONS IN SRESISTORS
S/N V(DC) I(MA) R(Ω)
1 12 2 47,000
2 11 3 2200
3 10 4 220,000
4 9 4 220,000
5 8 8 1000,000
6 7 2 330,000
7 6 1 330,000
The table 1.4 show above, is used in describe the current variation in the different
resistors the circuit which show in table 4.1 that the value of the resistor determine
the amount of current through the resistor with respect to input voltage in the
circuit.
Fig4,1. Circuit diagram of the ringer
4.1 TONE GENERATOR
The diagram of fig.4.1 is a diagram of the ringer that generates the ringing tone of
the intercom. Ringing tone is an audio tone that signal the user of one of the two
phones (e.g. unit 1) that the other user (unit2) wants to establish a conversation in
the network. The process ofgenerating the ringing tone involves researching on the
datasheet of top semiconductor manufacturers, to get a suitable IC (intergraded
circuit) for it. The semiconductor guide of Toshiba shows that the popular timer IC
NE555 is suitable since it can connected to function as an stable multivibration to
generate an audio frequency tone of 450HZ. The pin out of IC and are test circuit is
as shown below.
Fig. 4.3 APPLICATION CIRCUIT FOR THE 555 TIMER
The 555 monolithic timing circuit is a highly stable controller capable of
producing accurate time delays, or oscillation. In the time delay mode of operation,
the time is precisely controlled by external resistors (RA and RB) and capacitor( C)
For a stable operation as an oscillator, the free running with two external resistor
and one waveforms and the output structure can sourceor sink up to 200mA

26. specification from producershows that the IC operates at a voltage range of 5 to
15 volts (Geoffery E Lewis 1989).
4.4 CALCULATION
The frequency of oscillation is caculcate by using the formula below.
T1 = Time of ON = 0.693 (Ra+Rb)C
T2 = Time of OFF=0.693(Rb)C
Total time(T)=T1+T2
From the above expression, one can easily compute the frequency since it is the
inverse of time .hence F =1/T(hertz).
T1= 0.693(1000+2(15000)×100×10-9………………………………………(4.10)
T2=2.1483×10-3……………………………………………………………..(4.11)
F=1/2.1483×10-3……………………………………………………………..(4.12)
=465.48 ∞ 465Hz
The frequency of the oscillator is set to 465 hertz by using 1000 ohm as the Ra and
15000 ohms as Rb and 100 nanofarad as C.

31. AUDIO AMPLIFIER
In the fig. 4.4, electrical signal from the transducer (microphone) is considerably
little to be fed directly to the speaker. Moreover when electrical signal is being
transmitted over a long distance it degrades as it goes through the medium. Calls
for the introduction of an amplifier in this project. The amplifier section of this
work is built with popular low power consumption audio amplifier IC (TDA2003)
from Toshiba Semiconductors. The IC is not suitable for the work (Two way wired
Intercom) because of its low idle power consumption.
TABLE 4.2 BILL OF QUANTITY AND EVALUATION (BEME)
S/N COMPONENT QUANTITY
(X2)
INDIVDUAL
PRICE(N)
AMOUNT
(N)
1 NE555 Timer
IC
3 100 300
2 CI815 transistor 3 40 120
3 6Ω speaker 2 300 600
4 IN4001 Diode 4 10 20
5 47Ω 1 10 20
6 330KΩ 1 30 20
7 2200KΩ 2 10 40
8 2200kΩ 1 10 20
9 100kΩ 1 10 20
10 100uf 2 10 40
11 10nf 4 20 160
12 TDA Audio
Amplifer
1 400 400
13 12Ω Speaker 2 200 400
14 47µf(Electrolyte
Capacitor)
1 30 60
15 10nf 1 20 40
16 220nf 1 20 40
17 1µf 1 20 40
18 50kΩ Variable
Resistor
3 40 120
19 carbon 2 500 1000
20 Microphone 2 400 800
21 Battery 1 600 1200

32. 22 Packaging 2 700 2800
Total=8,260
CHAPTER FIVE
CONCLUSION AND RECOMMENDATION
5.1 LIMITATION OF THE STUDY
This work has encountered so many limitations just like any common but
advanced design, which includes;
II. This circuit is based upon theoretical calculations and may require
practical changes to be made while implementing the circuit in hardware.
III. This is designed for loudspeaker with low range and hence cannot be
used at large buildings.
IV. The most challenging is that of access to materials, for building the
project work.
5.2 CONCLUSION
It shall sound insolvent to say that the this project was achieved at a platter
of gold. The success ofthis work is a dividend of careful research, practical and
commitment; also it is a guarantee of a sound knowledge of electronics component
and its implementation in communication.
During the execution of this project, more knowledge were acquired which if this
kind of work is made a constant practice, the sky will be limit in the field of
electrical electronics, particularly communication and electronic option.
When much problem was encountered in this work was on the purchase of the
component since it was costly and some were even purchased at lagos at an
additional transportation costwhich increased the production cost. Considering
this, if the component purchases are made in bulk from the producer, this selection
of the trimmer for effective impedance matching at the output of the one unit input

33. of the second unit after the encountering such a difficulty. In addition , if a screen
cable cannot be used, a power line carrier communication can be engaged as the
transmission medium between the two spots where he PHCN wire cable can be
used as the medium for communications and this will reduce the productcost.
To costthis system for large industrial premises of other large premises, a
multiplexer controlunit with PC is incorporated to the system. Other technologies
associated to the system is the wireless where electromagnetic waves that carries
the information signal will be transtmitted through the air using an RF terminal and
convert it back to the original information through decoder. This technology
though costly but will make the intercom system more reliable and fixable just like
the handest. We belief that more research shall yield more innovation on this
technology to really make it stand the test of time.
5.2 RECOMMENDATION
Careful research and analysis has revealed the relevance of intercom system
in the various fact of our society. The importance of this facilities t human
Endeavour has outsmart the costof it productionbecause the implementation of
this technology will go along way to save costin the world of information
management, just like as the GSM technology is doing today. The relevance of this
technology ranges from domestic home utility (toilet, kitched, bedroom, doorgates
etc) industrial premise untility, security services utility, public service utility and
many more. It is rather unfortunate that the public has not gotten the orientation on
the utility of this diversified utility gadget due to the presence of the GS,M
supplement. The good news about intercom system is that it is not costintensive to
installed, it has no service costattachment.
The costinvolvement in this project actualization can be reduced by employing the
principal of mass production where component will be imported from the
production company in mass quantity and the gadget also produced in mass
quantity with different designs particularly in a reduced size.
There should also be such intercom system between the schoolsecurity units and
the students both in the lecture halls and schoolhotels should emergency calls both
securities of live and properties.

34. Our young engineering technocrats, government, NGO, financial houses to join
hands together and advance this country technologically by encouraging local
technology.