FEDERAL UNIVERSITY OF TECHNOLOGY OWERRI

A SEMINAR REPORT ON

“MULTI-PURPOSE CUSTOMER HELPS USING DTMF TECHNOLOGY”

WRITTEN BY

ONWUKWE UGONNA EZINWAREGD NO: 20081618963

(COMMUNICATION ENGINEERING OPTION)

APPROVED BY

MR. DIALA UCHENNA

SUBMITTED TO

ENGR DR. MBOCHA CHRISTIAN C

ELECTRICAL/ELECTRONIC ENGINEERING DEPARTMENT

IN PARTIAL FULFILLMENT FOR THE AWARD OF A BACHELORS DEGREE (B.ENG) IN ELECTRICAL/ELECTRONIC ENGINEERING

FEBRUARY 2013

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DECLARATIONIn partial fulfillment for the award of a Bachelors Degree (B.Eng) in Electrical/Electronic

Engineering, I, ONWUKWE UGONNA EZINWA (20081618963) hereby declare that the

work submitted in this thesis is my own, and any work that is not my own has been quoted and

acknowledged in the bibliography. This work has not been previously submitted for a degree at

the Federal University of Technology, Owerri.

MR DIALA UCHENNA DATE

(PROJECT SUPERVISOR)

ENGR. DR. F.K. OKPARA DATE

(HEAD OF DEPARTMENT)

(EXTERNAL EXAMINER) DATE

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DEDICATIONI dedicate this seminar report to The Almighty God who created heaven and earth, in his control

is everything and he is the most merciful.

This work is also dedicated to my parents Chief and Lolo Onwukwe, H.O for all their supports

and also to my unborn children. I say a very big thank you.

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ACKNOWLEDGEMENTI would like to extend my sincere gratitude to my research supervisors, Mr. Diala Uchenna for

his assistance and guidance towards the progress of this seminar. Throughout the year, Mr. Diala

Uchenna has been patiently monitoring my progress and guided me in the right direction and

offering encouragement. Obviously the progress I had now will be uncertain without his

assistance.

Most of all, I am very grateful to my family for their unfailing encouragement and financial

support they have given me over the years.

Last but not least, also to Mr. Akhidime, Oiseikhuemi for her constant encouragement during the

duration of this seminar preparation and report.

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ABSTRACT

The customer help system uses GSM phone interfaced to operate by application of Dual Tone

Multiple Frequency (DTMF) technology. This technology helps people to call a number and ask

for help on a product that is to be sold or services rendered by pressing the numbers in the

keypad of a phone. Each number pressed guides the user on a voice prompt which tells the

customer what to do. This application can be used by banks to check customers account balance.

It can also be used by schools so that students who want to check their results over the phone can

do so by entering their registration number and listening on the automated voice prompt. The

system is achieved using a GSM phone with an audio output terminal, a DTMF decoder circuit, a

micro controller and a computer system which is used for the storage of records to be retrieved

and a speech application using audio recording and playback. A SIM card is installed on the

phone attached to the computer so that when a user calls the phone number installed it is

automatically answered and the voice application starts running. The voice prompt welcomes the

user and asks for what services is to be rendered. It can be to check results, to check account

balance or to guide to user on what to do. The program running in the computer is designed

using Microsoft visual studio integrated development environment (IDE) while the

microcontroller program is designed using micro basic compiler.

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LIST OF FIGURESFig 2.1: DTMF that is generated when you press a button on the phone keypad.........................16

Fig 3.1: Block diagram representation of customer helps system using DTMF..........................20

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LIST OF TABLESTable 2.1: DTMF Row/Column Frequencies................................................................14

Table 2.2: A typical keyboard........................................................................................15

Table 2.3: DTMF values, Keypad Symbols.......................................................................18

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TABLE OF CONTENTDECLARATION….....................................................................................................2

DEDICATION……………………………………………………………………….3

ACKNOWLEDGEMENT..........................................................................................4

ABSTRACT............................................................................................................... 5

LIST OF FIGURES ....................................................................................................6

LIST OF TABLES…………………………………………………………………..7

TABLE OF CONTENTS .........................................................................................8

1.0 INTRODUCTION....................................................................................................10

1.1 SCOPE OF SEMINAR.................................................................................................11

1.2 AIM OF SEMINAR………………… .......................................................................11

1.3 OVERVIEW OF SEMINAR.....................................................................................11

2.0 GENERAL DTMF BACKGROUND........................................................................12

2.1 HISTORY OF DTMF…………..................................................................................12

2.3 PRINCIPLES OF OPERATION .................................................................................13

2.4 MICROSOFT VISUAL STUDIO ...............................................................................18

3.0 WORKING OF THE PROJECT .............................................................................19

3.1 BLOCK DIAGRAM REPRESENTATION………………………………………..21

3.2 EXPLANATION OF VARIOUS MODULES……. ………………………………… 21

3.2.1 MOBILE PHONES …………………………………………………………………21

3.2.2 DTMF DECODER……………………. ………………………………………………22

3.2.3 MICRO-CONTROLLER …………………………………………………………….22

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3.2.4 USB CONTROLLER ………………………………………………………………23

3.2.5 COMPUTER ………………………………………………………………….. 23

3.2.6 INDICATOR……………………………………………………………………….24

4 CONCLUSION AND RECOMMENDATIONS.............................................................25

4.1 CONCLUSION.................................................................................................25

4.2 RECOMMENDATIONS..............................................................................................25

REFERENCES.................................................................................................26

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CHAPTER ONE

1.0 INTRODUCTION

The customer help system uses GSM phone interfaced to operate by application of Dual Tone

Multiple Frequency (DTMF) technology. This technology helps people to call a number and ask

for help on a product that is to be sold or services rendered by pressing the numbers in the

keypad of a phone. Each number pressed guides the user on a voice prompt which tells the

customer what to do.

It makes use of the DTMF which act in this case as a decoder while the mobile phone attached to

the computer acts as the receiver. Ones the caller dials the number tied to the phone attached to

the computer, the system automatically answers and the coded message starts running.

Audios are attached to the system, by making it play on the background while the caller is been

asked to wait or guided what steps to be taken.

This has the advantage of reducing customer client confrontation and fostering good service

delivery.

The program running in the computer is designed using Microsoft visual studio integrated

development environment (IDE) while the microcontroller program is designed using micro

basic compiler.

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1.1 Scope of the Seminar

In this seminar, there are a number of different tasks that needs to be addressed to lead towards

the completion of the main project. These tasks are discussed briefly in the following sections

with more in depth information provided in later chapters as indicated.

1.2 Aim of the Seminar

The main goal of this seminar is see how DTMF can be used with the incorporation of Micro-

Controller to achieve an automatic response system for customer help services.

This will enable Electrical/Electronic Engineering Department (which will be used in the final

project) to assist her students in checking their results and any other things deemed fit.

1.3 Overview of the Seminar

The structure of this seminar is set out into four sections.

Chapter 1 gives an introduction to this seminar and a brief description of the different areas that

make up the seminar.

Chapter 2 will focus on the history, construction and principles of operation of the DTMF

decoder. The implementation of the software used for programming the Micro-Controller and

Computer in the main project are also discussed.

Chapter 3 will focus on the block-diagram representation with detailed explanation of each

module for the realization of the entire project.

Chapter 4 will give the conclusions of the seminar and suggests recommendations based on the

future works that could be done to expand on the final design specified in this seminar.11

CHAPTER TWO

2.0 General DTMF Background

Dual-tone-multi-frequency signaling is used for telephone signaling over the line in the voice-

frequency band to the call switching center. The version of telephone of DTMF used for

telephone tone dialing is known by the trade-marked term Touch-Tone, and is standardized by

International Telecom Union (ITU) Recommendations Q.23. Other multi-frequency systems are

used for signaling internal to the telephone network [1]

2.1 History of DTMF

In the time preceding the development of DTMF, telephone systems employed a system

commonly referred to as pulse (Dial Pulse or DP U.S) or loop disconnect (LD) signaling to dial

numbers, which functions by rapidly disconnecting and connecting the calling party’s telephone

line, similar to flicking a light switch on and off. The repeated connection and disconnection as

the dial pins sounds like a series of click. The exchange equipment counts those clicks or dial

pulses to determine the called number. Loop disconnect range was restricted by telegraphic

distortion and other technical problems, and placing calls over longer distances required either

operator assistance (operator used an earlier type of multi-frequency dial) or the provision of

subscriber trunk dialing equipment.

Dual Tone Multi-Frequency or DTMF is a method for instructing a telephone switching system

of the telephone number to be dialed or issue commands to switching systems or related

telephony equipment.12

The DTMF dialing system traces its root to a technique AT&T developed in the 1950s called MF

(Multi-Frequency) which was deployed by AT&T telephone network to direct calls between

switching facilities using in-band signaling. In the early 1960s, a derivative technique offered by

AT&T through its Bell System telephone companies as a “modern” way for network customers

to place calls.

The customer product was marketed by AT&T under the registered trade name Touch-Tone.

Other vendors of compatible telephone equipment called this same system “Tone” dialing or

“DTMF”.

The DTMF system uses eight different frequency signals transmitted in pairs to represent sixteen

different numbers, symbols and letter detailed below.

#, *, A, B, C, and D

DTMF tones are also used by some cable television networks and radio networks to signal the

local cable company/network station to do a local advertisement or station identification. Theses

tones were often heard during a station ID preceding a local advert inserts. Previously, terrestrial

television stations also used DTMF tones to shut off and turn on remote transmitters.

2.2 Principle of Operation

A DTMF signal consists of a mixture of two sine wave tones, often called the

row and column frequencies because of their correspondence to the layout

of the phone keypad [2].

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In DTMF there are sixteen distinct tones. Each one is the sum of two

frequencies: one from a low and one from a high frequency group. There are

four different frequencies in each group.

The phone only uses twelve of the possible sixteen tones. If you look at your

phone, there are only 4 rows (R1, R2, R3 and R4) and three columns (C1, C2

and C3). The rows and columns select frequencies from the low and high

frequency group respectively. The exact values of the frequencies are listed

below [3].

TABLE 2. 1: DTMF ROW/COLUMN FREQUENCIES [2]

LOW-

FREQUENCIES

ROW # FREQUENCY

(HZ)

R1: ROW 0 697

R2: ROW 1 770

R3: ROW 2 852

R4:ROW 3 941

HIGH

FREQUENCIES

COLUMN # FREQUENCY

C1: COL 0 1209

C2: COL 1 1336

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C3: COL 2 1477

C4: COL 3 1633

C4 not used in

phones

Thus, to decipher what one tone frequency is associated with a particular

key, look at your phone again. Each key is specified by its row and column

locations. For example, the key “2” is row 0 (R1) and column 1 (C2). Thus,

using the above table, “2” has a frequency of

770+1336=2106Hz;

The “9” is a row 2 (R3) and column 2 (C3) and has a frequency of

852+1477=2329Hz. [2]

TABLE 2.2: A TYPICAL KEYBOARD [3]

1 2 3 697

Hz

4 5 6 770H

z

7 8 9 852H

z

* 0 # 941H

15

z

1209

Hz

1336

Hz

1477

Hz

Figure 2.1: The DTMF tone that is generated when you press a button on the phone

keypad.

Engineers at then-mighty Ma Bell chose these tones carefully to ensure that none had a harmonic

relationship with the others and that mixing the frequencies would not produce sum or product

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frequencies that could mimic another valid tone. They specified that the tones be free of

distortion, and that the high-group frequencies (the column tones) be slightly louder than the

low-group to compensate for the high-frequency roll off of voice audio systems.

Because DTMF was devised in the days before you could hear a pin drop, it’s an exceptionally

noise-resistant signaling method. If a properly designed DTMF decoder thinks there’s a valid

DTMF signal present in some lousy audio, there almost surely is.

DTMF tones can represent one of 16 different states or symbols, as shown in Figure 2.1. That is

equivalent to four bits of data, also known as a nibble. Most DTMF decoders can process at least

10 tones per second under the worst of conditions, so DTMF can easily convey 40 bits (5 bytes)

of data per second. That’s nowhere near the performance of a good communications modem,

which can operate nearly 600 times as fast (28,800 bits per second), but it’s a lot more robust

under noisy line conditions.

Note that the numbers and symbols on the phone keypad don’t always match the binary values of

the DTMF nibbles. Most notably, the “0” on the keypad is represented in DTMF by a value of 10

(decimal) or 1010 binary. Table 2.1 summarizes the rest of the four-bit values [2]

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Table 2.3: DTMF Values, Keypad Symbols [2]

BINARY VALUE DECIMAL VALUE KEYPAD SYMBOL0000 0 D0001 1 10010 2 20011 3 30100 4 40101 5 50110 6 60111 7 71000 8 81001 9 91010 10 01011 11 *1100 12 #1101 13 A1110 14 B1111 15 C

2.3 Microsoft Visual Studio

Microsoft visual studio is an Integrated Development Environment (IDE) from Microsoft. It is used to develop console and graphical user interface application along with windows forms applications, websites, web-application and web services in both native code together with managed code for all platforms supported by Microsoft windows, windows mobile, etc.

It supports different programming languages. Built in language includes C/C++, VB.NET, etc. it consist of the code editor, debugger and designer.

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CHAPTER THREE

3.0 WORKING OF THE PROJECT

The working of the DTMF customer help system is explained below;

A call is made to the mobile phone (as receiver) attached to the computer. Now after answering

the call, and in the course of the call, if any button is pressed, control corresponding to the button

pressed is heard at the other end of the call. This tone is called dual tone multi frequency tone

(DTMF) and the computer receives this DTMF tone with the help of phone stacked in the

computer.

The received tone is processed by the microcontroller with the help of DTMF decoder. The

decoder decodes the DTMF tone in to its equivalent binary digit and this binary number is sent to

the microcontroller. The microcontroller is pre-programmed to take a decision for any give input

(from the caller) and outputs its decision to the computer in order for the computer to interpret

and return back the required or desired information to the caller.

The mobile that makes a call to the mobile phone attached to the computer acts as a remote. So

this simple customer help project does not require the construction of receiver and transmitter

units.

DTMF signalling is used for telephone signalling over the line in the voice frequency band to the

call switching centre. The version of DTMF used for telephone dialling is known as touch tone. 19

DTMF assigns a specific frequency (consisting of two separate tones and a high and low

frequency) to each key so that it can easily be identified by the electronic circuit. The signal

generated by the DTMF decoder is the direct algebraic submission, in real time of the amplitudes

of two sine (cosine) waves of different frequencies, i.e. pressing 5 will send a tone made by

adding 1336 Hz and 770Hz to the other end of the mobile.

3.1 BLOCK DIAGRAM REPRESENTATION

Below is the block diagram representation for the realization of the customer help system using

DTMF.

Fig 3.1: Block Diagram Representation of the Customer Help System using DTMF

3.2 Explanation of the various Modules

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The various modules making up the system are:

Mobile phone

DTMF decoder

Micro-controller

USB Controller

Computer with Audio programme

3.2.1 Mobile Phone

The mobile phone acts as a receiver. It is the interface between the caller (customer) and the

DTMF. The phone must make use of a SIM card owned by a network operator. Any mobile

phone operator or service provider can be used. The caller is required to call the mobile

phone attached to the DTMF for the system to work.

3.2.2 DTMF Decoder

The DTMF (also known as touch-tone) are the audible sounds you hear when you press keys

on your phone.

The DTMF decoder is a useful tool used for decoding DTMF generated by telephones. It

decodes the signal from the mobile phone into binary digits. The decoded digits are viewed

on a LCD screen. The DTMF decoder can be directly connected to a serial port to view the

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digits in HyperTerminal on a computer. The DTMF decoder stores the last 234 received

digits in Electrical Erasable Programmable Read Only Memory (EEPROM).

3.2.3 Micro-Controller

The micro-controller acts as an interface between the DTMF and the Computer (machine) via

the USB controller. Its function is to convert the binary digits of the DTMF into ASCII

(American Standard Code for Information Interchange)through the USB serial port

(Controller) recognized by the computer.

The micro-controller programme is designed using “micro-basic compiler”.

3.2.4 USB Controller:

The USB controller is the interface between the micro-controller and the computer. Its

function is to transmit the ASCII codes generated by the micro-controller for the computer to

read and act on. It acts as a SISO (serial input, serial output device).

3.2.5 COMPUTER:

The computer contains the already programmed messages with associated audio. It gives out

information based on the pre-programmed or pre-recorded information, detailing the step by

step action to be taken by the caller for the realization of the end objective.

It is programmed using the Microsoft visual studio integrated development environment

(IDE)

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3.2.6 Indicator:

The indicator displays the output of the DTMF

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CHAPTER FOUR

4.0 CONCLUSION AND RECOMMENDATIONS

4.1 CONCLUSION

The actual project is yet to be carried out but this seminar gives a useful insight on the feasibility

and workability of this project.

The use of the DTMF makes it easier and more economical as the cost of data transfer (without

the use of a service provider) may be too thereby making its achievement a mere wish.

Also, the micro-controller can be skipped in future projects as the DTMF (new ones) have the

ability to convert directly to ASCII, not requiring an interface, a normal IDE cable can be

connected from the DTMF straight to the computer.

4.2 RECOMMENDATIONS

There are a number of improvements on a larger scale I will like to recommend for future woks.

This seminar (and final implementation) is limited to just Electrical/Electronic Engineering

Department but future works should include:

The entire school (especially, for admission status checking and checking of results). This

will give not just the student but also the parents the ability and access to follow up the

growth and performance of their wards in school

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A staff-student relationship, which will enable each student access to speak to their

course advisers via the phone, and parents, can also easily contact their wards course

adviser.

I believe these are achievable, and the next crops of final year students should be tasked on

implementing it.

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REFERENCES

[1] John Iovine, 1995, “DTMF IR Remote Control System Nuts & Volts, Vol. 15, No.6.

[2] Scott Edwards, 1995, “DTMF “Touch” Tones are Music to the Ears of this Stamp Transmit/Receive Circuit”

[3] Cell phone operated land rover Electronics For You’ Magazine, Edition (July 2008)

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