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UNIVERSITI PUTRA MALAYSIA
INTERNET - BASED SECURITY AND MONITORING SYSTEM
ISAMELDIN MOHAMMED SULIMAN
FK 1998 10
INTERNET -BASED SECURITY AND MONITORING SYSTEM
By
ISAMELDIN MOHAMMED SULIMAN
Thesis Submitted in Fulfillment of the Requirements for the Degree of Master of Science in the Faculty of
Engineering Universiti Putra Malaysia
November 1998
To my parents and sisters
ACKNOWLEDGEMENTS
I would like to express my sincere thanks to my supervisor Dr. Abd Rahman
Ramli. This thesis would not have been done without his support, encouragement , and
comments. Thanks and appreciation is extended to the members of the supervisory
committee Dr. Mahmud Hassan and Mrs. Roslizah Ali.
I would also like to express my thanks to the staff at the Graduate School Office
for their help and cooperation. My appreciation and gratitude to all of the individuals at
the Department of Computer and Communication System Engineering , who had been
cooperative.
I gratefully ackno wledge the support of Ir. Dr. No nnan Bin Mariun the general
manager of Control and Automation System Center (CA SC ). My thanks and appreciation
to my colleagues at the CA SC for their help and suggestions during the research work.
iii
TABLE OF CONTENTS
Page
AC KNOWL EDG EM ENT S. . . . . ..... . ............ ............ .. . .. . .. . .... . ............. . III
LI ST O F T ABL ES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v u
LI ST O F FIG URES ......................................................... ........... .... Vlll
LI ST O F ABB REVIATION S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
AB ST RACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x u
AB ST RAK . . . . . . .......... .................. .. ... ..................... .............. ..... .. . . XIV
CHAPTER
I INT ROD UCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Benefits ofa Web-Based Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Objectives . . . . . . . . .. . .. ... . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . ... . ... 3
Thesis Organisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
II REVI EW ON SEC URIT Y SYST EM S A ND
A LA RM SIGNA LLING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Security and Monitoring Technology .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Intrusion Detection and Monitoring Systems . . . . . . . . . . . . . . . . . . . . . . . . . 8
The Internet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1
Internet Telephony . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3
III BAC KG RO UND TH EO RY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5
Java Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 5
Telephone Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6
The Phone Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
IV
On-hook and Off-hook Operation ........................... 17
DTMF Dialing .................................................. 19
TP5088 DTMF Generator .................................... 20
Telephone Line Interface ...................................... 22
Modems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
PC Serial Interfacing ................................................... 23
PIC16C8 4 Microcntroller .............................................. 24
IV SYSTEM ARCHITECTURE ........................................... 25
Introduction ............................................................... 25
General Layout of the Security System ............................. 25
Software Description .................................................... 27
Interface to the Host Machine ................................. 27
Interrupts ........ ................................... ............ ... 27
Data Exchange between C Program and Java Applet ..... 28
The Web Server Installation ............................................ 29
The Communication Program ......................................... 30
Implementing the Interrupt Service Routine (ISR) ................. 31
Creating the Monitor Server ............................................ 34
Implementing the Monitor Client Applet ............................ 37
The infotist Applet ....................................................... 39
HTTP Links to Monitored Locations Applet .. ...................... 42
The Password Apple .. ...... ..... ............ .................. ... ..... ... 44
The Chat System .......................................................... 46
Creating Multithread Chat Server........ ................. ... 47
Building Chat Client Applet ................................... 50
Conclusion ................................................................ 54
V RESULTS AND DISCUSSION ......... ......... . ... .............. . ... 55
System Performance ........ .................... ...................... ... 55
Conclusion ................................................................ 62
v
VI CON CLUSION S AND RECOMMENDA nON S ................. 63
Conclusions ............................................................... 63
Recommendations and Directions for F uture Work s ............ 66
Sensors Unit ...................................................... 67
Control Unit ..................................................... 67
Auto-Dialler Unit ................................. ............ 68
Data Access Arrangement (DAA) ............................ 68
REFERENCES . . . . . . . . . . . . . . ..... .. ... . . . . . . . . . . . . .. .. . .... ... . . . . . .. ... . . . . . . 7 1
APPENDICES .. . . . . . . . . .. . . . . . . . . . .... .. . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . 7 5
A The Communication Program......... ... .................... 7 6
8-1 The Monitor Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 9
8-2 The Monitor Client Applet ............... ....... .... ...... .... 8 3
C The Infolist Applet ............................................ . 9 0
D HTTP Link s Applet ............................................ 9 7
E The Password Applet .......................................... 9 9
F -1 The Chat Server ................................................ 102
F -2 The Chat Client Applet ..... ............. ...................... 107
VITA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
vi
LIST OF TABLES
Table Page
1 DTMF Digits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2 Functional Truth Table of TP508 8 DTMF Generator.... . . . 21
vii
LIST OF FIGURES
Figure Page
1 On-hook State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2 Off-hook State .................. ......... ... ...... .................... . ..... 18
3 General Layout of the Security System .............................. ... 26
4 Mechanism for Data Exchange between Java
Applet and C Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5 Algorithm for Implementing the Interrupt Service Routine . . . . . . . . . 32
6 The Communication Program F lowchart . . . . . . . . . . . . ............ ... ... 33
7 Algorithm for Creating the Monitor Server . . . . ... . . . . . . . . . . .. ... . . . . . 35
8 The Monitor Server F lowchart . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . ... .. . 36
9 Algorithm for Creating the Monitor Client ............................. 38
10 The Monitor Client F lowchart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39
11 Algorithm for Infolist Applet . . . . . . . . . . . . . . . . . . .. . .. . . ... .. . . . .. . . . . . . . . . 40
12 The Infolist Applet F lowchart . . . . . . . . . . . . . . . . . . . . . . . . .............. ..... 41
13 The HTTP Link s Applet F lowchart . . . . . .. ... . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
14 The Password Applet F lowchart . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. . . 45
15 The Chat Client/Server Pair . . . . . . . . . . . . .. . .. . . . . . . . . . . . .. . . . . . . . . . . . . . . . 47
16 Algorithm for Creation of the Chat Server . . . .. . . . . . . . . . . . . . . . . . . . . . . . . 48
17 The Chat Server F lowchart . . . . . . . . .. . . . . . . .. . . .. .. . . . .. . . . . . . . . . . . . . . . . . . 49
18 Algorithm for Building the Chat Client Applet . . . . . . . . . . . . . . . . . . . . . . . . 52
19 The Chat Client F lowchart . . . .. . . . ... . . . . . . . . . . . . . . ...... .. ............. 53
Vlll
20 The Password Applet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
21 Applet s Execut ion Using Int ernet Explorer 4.01 . ... ... .. .. ...... .... 58
22 Applet s Execut ion Using Hot Java Browser. ...... .. .... ... ......... ... 58
23 Applet s Execut ion Using N et scape N avigat or Gold 3.01 ..... ... .... 59
24 Chat Server Response t o Chat Client s .... .. . . . . . . . . . . . . . . . . . . . ... . . . ... 60
25 The Chat Client Applet . . . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
26 Block Diagram of t h e Proposed Monit oring Device 67
ix
LIST OF ABBREVIATIONS
AC Alternating Current
AWT Abstract Windowing Toolk it
CCTV Closed-circuit TV
CGI Common Gateway Interface
CPU Central Processing Unit
DAA Data Access Arrangement
DC Direct Current
DCE Data Communication Equipment
DLAB Divisor Latch Access Bit
DTMF Dual Tone Multi-frequency
DTE Data Terminal Equipment
DTR Data Terminal Ready
EOI End of Interrupt
F IF O F irst In F irst Out
GUI Graphical User Interface
HTML Hypertext Mark up Language
HTTP Hypertext Transfer Protocol
IER Interrupt Enable Register
IRQ Interrupt Request
ISR Interrupt Service Routine
x
JV M
LAN
LED
MSR
OOP
PC
PIC
PSTN
PWS
RI
RISC
ROM
RTS
RTU
SCADA
TCPIIP
UART
URL
WWW
Java V irtual Machine
Local Area Network
Light Emitted Diode
Modem Status Register
Object Oriented Programming
Personal Computer
Programmable Interrupt Controller
Public Switched Telephone Network
Personal Web Server
Ring Indicator
Reduced Instruction Set Computing
Read Only Memory
Request To Send
Remote Terminal Unit
Supervisory Control And Data Acquisition
Transmission Control ProtocollIntemet Protocol
Universal Asynchronous Receiver/Transmitter
Uniform Resource Locator
World Wide Web
Xl
Abstract of thesis submitted to the Senate of Universiti Putra Malaysia in fulfilment of the requirements for the degree of Master of Science.
INTERNET-BASED SECURITY AND MONITORING SYSTEM
By
ISAMELDIN MOHAMMED SULIMAN
NOVEMBER, 1998
Chairman: Abd Rahman Ramli, Ph.D.
Faculty: Engineering
This study describes a remote monitoring and security system based on the
Internet. It is intended to investigate the possibilities of using the integration of the
Internet and telephone lines in providing solution to security problems by
conveying alarm signals from remote monitored locations. A homepage was
developed to allow selected users to get monitoring and security information. A
special purpose web server was designed to handle the system. This web server
which is acting as a central monitoring station will supply the system's users with
information reporting any intrusion at remote monitored locations
The system utilised the existing telephone network , which is cost-effective
and user friendly in alarm transmission from remote monitored location. An internal
modem was used to maintain interface between the telephone line and the web
server. A communication program developed using C language was responsible for
xii
data capturing from the modem through the serial port and providing them to the
web server. Java language was used for developing a server program that is running
in the back ground to enable data provided by the communication program to be put
on the Internet for access. A graphical user interface (J ava applets) was
implemented to allow users to access the system.
The results of applying this approach showed the possibilities of using the
integration of the Internet and telephone lines in conveying alarm signals and
control command. It also emphasised the import ance of Java language in
developing software programs for Internet-based systems. F urthermore, C language
is still required to fill the low-level interface gap that was not supported by Java
language. F inally, the application described in this study demonstrated that the
Internet can be used not only for information exchange and retrieval, but also used
as a communication medium for monitoring and controlling of remote physical
environments.
xiii
Abstrak tesis yang dikemukan kepada Senat Universiti Putra Malaysia untuk ijazah Master Sains
SISTEM KESELAMATAN DAN PEMANTAUAN BERASASKAN INTERNET
Oleh:
ISAMELDIN MOHAMED SULIMAN
NOVEMBER, 1998
Pengerusi: Abd Rahman Ramli, P.hD.
Fakulti: Kejuruteraan
Kajian ini menerangkan satu sistem pemantauan dan keselamatan jarak jauh
menggunakan internet. Tujuan kajian adalah untuk menyiasat kemungkinan
menggunakan integrasi talian telefon dan Internet untuk menyelesaikan masalah
keselamatan dengan menghantar isyarat penggera dari lokasi jauh. Halaman web
dibangunkan untuk membenarkan pengguna mendapatkan maklumat bagi pemantauan
dan keselamatan. Komputer perumah (pelayan WWW) bertindak sebagai stesen
pemantauan pusat yang menyediakan kawalan keselamatan dan laporan maklumat
keadaan sistem pengguna di lokasi pemantauan pada jarak jauh. Satu pelayan web dibina
khusus untuk mengawal sistem ini.
Sistem ini menggunakan rangkaian telefon yang sedia ada, yang mana ia lebih kos
efektif dan senang dipakai dalam penghantaran isyarat penggera dari lokasi jauh. Satu
modem dalaman digunakan untuk mengantaramukakan tali an telefon dengan pelayan
web. Program komunikasi yang dibangunkan dalam bahasa C bertanggungjawab untuk
xiv
mendapatkan data dari modem melalui pangkalan bersiri dan menghantar data itu kepada
pelayan web. Bahasa Java digunakan untuk membangunkan satu program pelayan yang
lari pada latar belakang supaya data yang diberi oleh program komunikasi boleh
dipaparkan pada internet untuk dicapai. Satu pengantara bergrafik (Java Applet)
dibangunkan supaya pengguna boleh mencapai sistem tersebut.
Keputusan daripada perlaksanaan kaedah ini menunjukkan kemungkinan untuk
mengguna integrasi internet dan talian telefon dalam menghantar isyarat penggera dan
arahan kawalan. Ia juga menitikberatkan kepentingan bahasa Java dalam pembangunan
peri sian untuk sistem berasaskan internet. Selanjutnya, bahasa C masih diperlukan untuk
memenuhi ruang aras rendah yang tidak dapat dilakukan oleh bahasa Java. Secara
kesimpulan, kajian yang diterangkan ini telah membuktikan bahawa internet boleh
digunakan bukan hanya kepada pertukaran maklumat dan capaian, tetapi ianya boleh
digunakan sebagai perantara komunikasi untuk pemantauan dan kawalan persekitaran
fizikal pada j arak yang j auh.
xv
CHAPTER I
INTRODUCTION
Computer network s and data communications are of great importance in today's
information society. Data communications is used to extend the power of computers and
allow computer facilities to be accessed at remote sites. The emergence of advanced
network ing capabilities and the availability of software and information components
mak es it easier to implement network ed data acquisition systems that is used to support
a wide range of applications lik e telemedicine (Koblas and Stienbak k , 19 9 4) ,
teleconferencing (Kirstein, 19 9 4) , control (Rovetta et at., 19 9 6) , and industrial
applications.
Within the Internet, the World Wide Web (WWW) has become the standard
integrative platform to access Internet services. It provides an effective mechanism for
distributing and sharing information. WWW offers a suitable infrastructure that integrate
computer-based services from multiple platforms and provides flexible and effective
tools for examining and monitoring remote physical environments. The adoption of new
Web-based systems will allow for higher level of interaction between users at remote
clients and servers.
2
The design and installation of security systems employs a wide variety of
techniques, often involving special types of equipment and materials designed for
specific applications (Traister, 1990). Advanced electronics has allowed security
systems to become highly efficient and flexible. Alarm signal transmission is the most
import ant part of an intruder detection system, therefore different types of
communication systems have been used for alarm signalling. Telephone lines over the
years have proved extremely reliable which provides a practical solution consistent with
both security and costing. Moreover, the introduction of microcontrollers will increase
the security considerably.
The work described in this study is an attempt that has been made to use the
integration of the Internet and telephone lines in security systems. The intense interest in
propert y protection and personal safety has made security systems highly desirable.
Monitoring services are needed for several reasons; some of which include house
location, away of home, or the desire of greater peace of mind.
The thesis outlines an approach used to build reasonably interactive security
system, which uses WWW-downloadable Java applet that interact with remote server. It
presents the benefits brought and limitations imposed by using the WWW and Java
language in developing real-time applications. The security system is a tangible example
of how modem technology can be used to provide security services.
3
Benefits of a Web-Based Environment
Within the past few years, the profile of the Internet has changed from that of
network connecting modest number of research institutions to a back bone connecting
individuals, government agencies, an d corporations in an emerging information
infrastructure (Larnm and Reed, 1 996) . The rapid growth of the WWW made it the most
convenient way to access information in the Internet. Moreover, the emergence of Java
language as an effective tool for extending functionality and improving performance of
the Web will facilitate utilising the Internet in building real-time applications.
The protection of property against attack s is the aim of any security procedure.
Many types of security systems are used to support protection of human property, which
range from private protection (homes) to public protection (firms) . These systems are
continuously scanning the area under monitoring, look ing for intruders and reporting
whenever intrusion is detected. Integrating this type of systems in the Internet, which has
the ability to provide many services (communication, multimedia capabilities, etc.) will
enhance security system in several ways. F or example, the multimedia capability of the
Internet could be used to supply visual and audio information to a security guard at a
central monitoring station as well as security system users around the world.
Objectives
The objectives of the Internet-based security and monitoring system are as
follows:
4
1. To investigate the possibilities of using the integration of the Internet and telephone
lines in providing solution to security problems by conveying alarm signals from
remote monitored locations.
2. To establish a web server that acts as a central monitoring station to receive alarm
signals and to enable information to be put on the Internet for access.
3 . To implement a graphical user interface (Java applets) to allow users to access the
web server.
Thesis Organisation
The thesis consists of six chapters. Chapter I presents a short introduction and
objectives of the project. In Chapter II a literature review on security systems and alarm
signalling is provided. Chapter III gives theoretical back ground of the tools that are used
in building the system. Chapter IV gives a general description of the system. It also
provides methods used for the software development. The system's performance and
results are discussed in chapter V . Finally, the thesis is concluded in Chapter V I, which
summ arises the conclusions and directions of future efforts.
CHAPTER II
REVIEW ON SECURITY SYSTEMS AND ALARM SIGNALLING
Introduction
The need for security systems in all types of buildings becomes a necessity with
the increase in crime rate. Alarm and monitoring systems can be used to prevent crime.
By protecting places such as homes, office, and buildings using alarm systems, security
guards and patrol officers can spend more time in areas with high crime rates and with
fewer premises protected by alarm systems. This chapter will review the components of
security and monitoring systems, and illustrate different methods and techniques that
have been used in designing and building of security systems.
Security and Monitoring Technology
Security and monitoring systems were originally introduced as a means to protect
people and property by drawing attention to a problem in its beginning stages so that the
problem can be controlled through quick action. The use of electricity and electronics in
the fight against crime is not new. When electricity was put to practical use around the
5
6
later part of the last century, methods were devised to use door bells, entrance detectors,
and manually operated fire alarms for signalling devices (Traister, 1990). In 1858,
Edwin began the first central office burglar alarm system (Cunningham, 1988).
The two basic signal circuits that were used for security and fire alarm systems
are open and closed circuit. The advantage of the open circuit technique was the reduced
cost in providing alarm protection. However it has certain drawback as a wire to one of
the sensors could be cut and there would no means of detecting it. To avoid difficulties
of the open circuit (Capel, 1989), the closed circuit technique came into general use. In
the early 1960s, closed circuit TV (CCTV) was introduced (Fennelly, 1997) to provide a
useful supplement to an intruder alarm system, particularly in large building complexes.
In an effort to improve security systems, multiplexing circuits were used to transmit
multiple alarm signals using a common carrier. Another major improvement in security
systems was the change from analogue to digital data transmission which made it
possible to apply the capabilities of digital computers for security systems (Hopf, 1979).
Security alarms consists of several functional parts. Sensors to detect the action
or penetration of an intruder, control unit that is used to receive, process and transmit
alarm signal to a central station, communication medium, and a central monitoring
station that operates for 24 hours a day to supervise, record, and maintain alarms
(Fennelly, 1997). When an alarm or monitoring information is to be transmitted, the
medium of communication can be in the form of:
7
1. Power line. The power mains are used to transfer alarm signal from the monitored
locations to the central station. The use of power lines as the transmission medium in
a facility could significantly reduce cabling costs (Halbig, et at., 1994).
2 . Cabling. A dedicated cabling system is run from the protected location to the central
monitoring station. The disadvantage of the direct cabling system is the high cost of
the dedicated line.
3. Telephone. The most common cost-effective form of alarm monitoring has been via
telephone lines. If an alarm device wishes to communicate with the central station, it
will instruct the dialler to dial the monitoring station reporting the alarm
information.
4. Radio signal transmission. This method takes the alarm signal from the protected
locations and sends it via radio frequency to a central monitoring station.
Supervisory Control And Data Acquisition (SCADA) is an industrial
measurement and control system consisting of a central host usually called a master
station, one or more remote terminal units (RTU) , communication medium and a
collection of software used to monitor and control remote located data field elements.
SCADA applications includes monitoring and control services for fire, security, building
management as well as meter reading and control for utilities such as gas, water and
electricity. The overall performance of SCADA system depends on satisfactory
performance of the integral data communication links (Bruce and Lee, 1994). SCADA
covers large geographic areas and rely on variety of communication interfaces between
RTU's and the master station. Transmission of data could take place over the power
8
line, radio frequency link, twisted pair network in addition to a normal telephone line.
The data acquisition is accomplished by RTV's scanning the field input connected to the
R TV to detect alarm conditions, and if an alarm is detected it will be sent to the master
station. SCADA carry out all necessary analysis and control, and then display this data
on a number of operator screens.
Intrusion Detection and Monitoring Systems
In the past, security systems that implemented CCTV were forced to use
expensive television equipment. However, Christoffersen (1990) showed that the PC
based CCTV system is a highly functional alternative to conventional video system
equipment as it could offer reduced cost and reduced amount of software and hardware
maintenance besides the equipment is of compact size. According to Barry (1993),
improved capacity links have enabled the development of high data sensors such as
remotely controlled camera and imaging units. Laura (1994) showed that a storage area
can be monitored by collecting a basis image representing the monitored area and then
continuously monitoring the area to detect changes in the monitored area.
In many video surveillance applications used for intrusion detection, a variety of
factors lead to some errors like varying illumination conditions, small camera motion,
rain, etc. Michael, et al. (1996) solved these problems by applying compression
techniques to transmit video images to a surveillance centre using digital network.
Although sending video images to the central monitoring station eliminates false alarms
9
by allowing central station operators to see what is happening inside the protected area,
the video images and detection results have to be transmitted to the surveillance centre.
Therefore an individual transmission channel is required for each sensor connected to
the monitoring centre. In addition, as the video signal is transmitted, the connection
needs high bandwidth, as a result the costs increase with the distance and number of
connections.
Centralised monitoring and security systems have been in use for many years but
increasing demands for expansion, flexibility and system integrity along with the cost
have exceeded the capabilities of the traditional systems. Key to the establishment of
security systems is a robust and well designed communications network. However. a
separate communication networks for security only is expensive and not necessary
(William, 1989). A new concept has been developed which allows for sharing resources
to provide security measures in a cost-effective manner. The most important resource
which may be shared is the data network. Johnson, et al. ( 1994) developed a remote
monitoring system by utilising network cable to collect data from sensors and store them
in storage medium. These data are remotely monitored via telephone. They concluded
that number of technologies could be combined to introduce new approaches to provide
unattended remote monitoring of facilities.
Another technique of alarm signalling is the utilisation of optical fibres which
are used to communicate restricted data, transmit CCTV pictures and detect intruders
moving across restricted areas. Hawkes ( 1995) described a study on a fibre optic