INTERCOM
Ahmed Salar
Malik Moazzam Ali
31 DEC 2018
Department of Electrical and Computer Engineering
COMSATS University Islamabad LAHORE CAMPUS
Declaration
“No portion of the work referred to in the dissertation has been submitted in support of an
application for another degree or qualification of this or any other university/institute or other
institution of learning”.
MEMBERS’ SIGNATURES
ii
Acknowledgements
My profound gratitude goes to ALLAH Almighty for his grace upon my life. We are 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 ALLAH bless you all ameen. My gratitude also
goes to my family members for always being there for me, especially to my brother for his
support and also my parents for their parental guidance I cannot thank you people enough but
keeping asking ALLAH to keep you all healthy with long life to reap the fruit of your labour
Ameen.
iii
Abstract
Intercom is a two directional communication system.it provides a reliable communication line
and is very easy to implement.the circuit is prepared by an amplifier,two mic’s and two
loudspeakers.we can extend this circuit by adding more number of speakers with the help of
switches.IC LM 386 works as a power output amplifier in this intercom circuit.LM386 provides
almost 2 watts of audio power via 15 volts supply voltage.this intercom circuit is very simple
and can be implemented in houses and offices.
iv
Table of contents
1
INTRODUCTION ............................................................................................................... 1
2
DESIGN ............................................................................................................................... 1
3
MEDIUM ............................................................................................................................. 1
4
FINAL PRODUCT .............................................................................................................. 1
5
PRACTICAL EXAMPLES ................................................................................................ 1
v
Table of Figures
FIGURE 2-1 FUNCTIONAL REQUIREMENTS NUMBERINGОШИБКА!
ЗАКЛАДКА
НЕ
ОПРЕДЕЛЕНА.
FIGURE 2-2 ARCHITECTURE OVERVIEW DIAGRAM ...... ОШИБКА! ЗАКЛАДКА НЕ ОПРЕДЕЛЕНА.
FIGURE 5-1 EXAMPLE FIGURE FOR PROTOTYPE APPLICATIONОШИБКА!
ЗАКЛАДКА
НЕ
ОПРЕДЕЛЕНА.
FIGURE 6-1 EXAMPLE FIGURE FOR USER INTERFACE .. ОШИБКА! ЗАКЛАДКА НЕ ОПРЕДЕЛЕНА.
vi
1 Introduction
An
internal
communication
system
is
a
system
that
basically
transfers
information in the form of electrical signal from one spot to 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
facilitates
intercom
the
is
exchange
also
of
a
personal
messages
between
telecommunications
two
or
more
device
which
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 .mode a 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)
1.1BACKGROUND 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 bedroom doing his or her school work, and wants to know when
dinner will be ready. May be the person is 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.
Two way wired intercom systems enables sound or speech to be transmitted in
two
directions,
therefore
enabling
a
conversation.
Intercoms
are
generally
compared of fixed microphone/speaker units which connect to a central control
1
panel.
In
transmitter
general,
a
a
communication
propagation
medium
system
and
requires
a
receiver.
three
The
things
namely;
information
to
a
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 form and so on).
1.2PURPOSE
(1) The main objective of this project is to construct a two way wired intercom
that will help two persons or more to communicate with each other within a
particular domain, like offices homes, warehouse etc.
(2)
To
immensely
help
the
engineering
students
understand
the
technology
behind two way simple intercom and its practical development
1.3SIGNIFICANT 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 door phone, connecting from the house to the door to screen visitors
to the 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
1.4SCOPE OF PROJECT
The scope of this 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;
The small signal amplifier must provide an undistorted
buffer amplifier to be able to drive a speaker of 8 ohms impedance
2
signal
into
the
2 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 diagram
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.

A Microphone

6 Volts of power (either from 4 'AA' batteries or a DC power supply)

2KΩ-6KΩ resistor (depending on the microphone in use)

10Ω resistor

10KΩ potentiometer

2 10μF electrolytic capacitor

100μF electrolytic capacitor

0.1μF ceramic capacitor

47nF ceramic capacitor

3.5mm audio plug
Table 2-1
3
Figure 2-2
Terminals 1 and 8 represent the gain control of the amplifier. These are the terminals where
you can adjust the gain by placing a resistor and capacitor or just capacitor between these
terminals. In this circuit, we will place a 10µF capacitor between these terminals for the highest
voltage gain. You can adjust this as necessary to adjust the gain, as needed.
Terminals 2 and 3 are the sound input signal terminals. These are the terminals where you
place the sound which you want to amplify. In our case for this circuit, the condenser
microphone will be connected to these terminals. Terminal 2 is the -input and Terminal 3 is the
+input. In our circuit, the positive microphone terminal will be placed on terminal 3 and
terminal 2 will be connected to the negative microphone terminal, tied to ground.
Terminal 4 is GND (ground). This is where the negative voltage of the power source connects
to.
Terminal 5 is the output of the amplifier. This is the terminal in which the amplified sound
signal comes out.
Terminal 6 is the terminal which receives the positive DC voltage so that the op amp can
receive the power it needs to amplify signals.
Terminal 7 is the Bypass terminal. This pin is usually left open or is wired to ground
4
2.1 PREPARING THE VEROBOARD
This work completed by using a veroboard to assemble the above explained
electronic components
2.2 SOLDERING
Soldering
between
is
the
certain
process
metals
of
by
making
joining
a
them
sound
electrical
with
a
soft
and
mechanical
solder.
This
is
joint
low
temperature melting point alloy of lead and tin.
2.3INPUT SOURCE (MICROPHONE)
The
input
source
is
the
mic
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.
2.4 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
reproduce
the
equivalent of the electrical signal being transmitted. This device is the speaker.
3 MEDIUM
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 copper cable as in electrical
5
signal. The medium through which the data is being transmitted in this project is
flexible wire
5 Final product fig 5-1
6
6 Practical Application:
Wiring intercoms
1980s MirTone intercom system
While every intercom product line is different, most analogue intercom systems have much in
common. Voice signals of about a volt or two are carried atop a direct current power rail of 12,
30 or 48 volts which uses a pair of conductors. Signal light indications between stations can be
accomplished through the use of additional conductors or can be carried on the main voice pair
via tone frequencies sent above or below the speech frequency range. Multiple channels of
simultaneous conversations can be carried over additional conductors within a cable or
by frequency- or time-division multiplexing in the analogue domain. Multiple channels can
easily be carried by packet-switched digital intercom signals.
Portable intercoms are connected primarily using common shielded, twisted pair microphone
cabling terminated with 3-pin XLR connectors. Building and vehicle intercoms are connected in
a similar manner with shielded cabling often containing more than one twisted pair.
Digital intercoms use Category 5 cable and relay information back and forth in data packets
using the Internet protocol architecture.
Four-wire broadcast intercoms
7
A modern four-wire intercom system capable of 272 sources and destinations manufactured by
Telex Communications Inc.
In the mid-90s four-wire technology started gaining more prominence due to the technology
getting cheaper and smaller. Four-wire circuit technology had been around for quite some time
but was very expensive to implement. It usually required a large footprint in the
physical television studio, thus was only used at very large television stations or television
networks.
8