Susceptible To EMI Interference Computer Science Essay

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This assignment is for Enterprise Networking subject that is one main module in International Advanced Diploma in Computer Studies of December, 2010 Examination. All contents in this assignment are based on Communication Network. This more prefers to make executive decision because of end of each task (recommendation). This assignment consists of 6 portions.

Task 1: It emphasizes on the network topologies (Star and Bus) and transmission media (UTP cable and Wireless Medium)

Task 2: This task is based on Internet Connection and Connection Speed by comparing services and cost on 2 Internet Service Providers.

Task 3: This task explains how two-way voice communication work by examples (walkie-talkie and GSM). Then it includes recommendation by comparing these 2 ways on their limitations, cost and features.

Task 4: It includes about 2 telephone systems by comparing their features, costs and equipments.

Task 5: It includes about the measures that would put to allow the continuous operations of Fire Department (Solar Energy, Emergency Flash Light and Satellite Phone).

Task 6: This task is report on details of overall tasks including estimated costs throughout and executive summary.

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Star topology

This topology is the most typical and practical network. It can be often seen in Client/Server network. In this topology, each node maintains an individual connection to a server (switch) for handling or routing. Data traffic between two nodes only goes through the switch. It does not pass or interrupt other nodes. This makes the network more redundancy i.e., One faltering connection to server will not cause the whole network to breakdown. Moreover, the network gains more data privacy i.e., the data travel with unique destination address.

Bus topology

This topology is the most simplistic topology. The clients of the whole network connect to a main communication Bus. As incoming and outgoing from every nodes pass through one single link, there may be more traffic and can occur data collision. Although intended node can be received data from the bus with unique address, data being sent will travel to every node on the bus. This shows the lack of data privacy to network.


Wireless medium


Can avoid from considering the structure of the building

Can avoid from the complex cabling

Can use portable stations even phone or PDA

Acceptable cost for wireless devices and reduce maintenance cost


Will not be best if the department is too big

Less security than cable network

Cable medium (Unshielded Twisted Pair)


UTP can be installed easily

UTP is available in local market easily and most widely by technicians

least expansive


Susceptible to EMI interference

It can be complex in cable when more stations

Will need regular maintenance


By revising above network information, the star topology with wireless medium is recommended to use for the Fire Department.

Why star topology is because of two basic reasons: performance and simplicity. It is easier to manage and troubleshoot. By replacing the switch with router, we can get Fire Department that covered with wireless network. With cable medium, the more stations will need for more users. But with wireless medium, each one in this department can access the network even with phone.


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It will be essential service for organization on critical circumstance. As this is the headquarters, it needs to know all latest news about fire alert on time. Newsfeeds can provide this kind of communication. Although this can be through phone line, the phone line can be busy or break down.

Electronic mail

Besides newsfeeds, another important service is electronic mail (e-mail). It is important when receiving reports, advisory letter and sending notice and other official letters to other department.


The 512 kbps broadband may be adequate because the users in the department will simply use the internet for e-mail and look for information. They rarely need to download files. It is roughly ten times faster than a dial up connection despite being the slowest broadband. The department will be convenience of using internet services for the lowest price.


BAGAN Net Internet Service Provider

This ISP targets on the home users and medium size organization. It handles the premium package such as internet browsing and e-mail services. The services are not insurance for 24 hours and the charge is also cheaper than other ISPs.


The YADANARBON Teleport provides the enterprise services and the charge is also expensive. This ISP ensures that the 24 hours services and returns charge if absence. There are more available choices in types of connections and speeds, so users can choose widely.


Although the higher price of the YADANARBON Teleport, we recommended this ISP for 24 hours services. The fire department has to connect the internet for 24 hours; the connection should be broken down for critical circumstances. The prices charged of internet connection optimized for this Fire Department are described below.


Activation FEE

Monthly FEE

Annual FEE

Modem FEE


512 kbps broadband line

1,400,000 Kyat

60,000 Kyat

60,000 Kyat

100,000 Kyat

E-mail & Internet Services

Own Domain Name Register


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Among limited technologies in two way-voice radio communicating, we would like to present two technologies/methods that Fire Department could implement. They are GSM (Global System for Mobile communication) and walkie-talkie (Public Trunked Mobile Radio).


GSM (Global System for Mobile communication)

It is full duplex communication and operates in between 800-MHz and 900-MHz frequency bands. It is also known Group Special Mobile. GSM operates in carves with 200-kHz band into eight TDMA (Time Division Multiple Access) channels. Each TDMA channel supports 33.8 kbps generally and 13 kbps for voice call.

GSM offers SIM for the security. SIM means Subscriber Identification Module (SIM), which plugs into a card slot in the handset. This SIM can be set up in any GSM set.

Walkie-talkie (Public Trunk Mobile Radio)

Walkie-talkie, one of the enhanced technologies from the Specialized Mobile Radio (SMR), is also known as a handheld transceiver. It supports half duplex communication. Although walkie-talkie works through 80 MHz generally, it enables users to search manually various frequency channels.

The concept of walkie-talkie and SMR is simple. The base station places a radio tower with Omni directional transmit/receive antennas. This tower should be on the highest point in the communication area and blasts the radio signal at the maximum power level that is allowable tower. The average coverage area of a standard radio tower is about 40 km in radius.

In walkie-talkie, the talker must depress a key or button on the microphone to talk and must release it to listen. This procedure is known as the Push-To-Talk (PTT) protocol. In order to know the other to talk, the special words such as "Over" or "Out" has to put at the end of the conversation.


Legal requirements for GSM

Within our country, to use or hire GSM communication for individually and organization in public, there has to submit forms to the MPT (Myanmar Post & Telecommunication). After submitting forms, the allowance letter will be sent to us from the Post Office within 2 or 6 months together with invoice. After payment to this invoice, the MPT will give SIM (Subscriber Identification Module) card and contract of hiring within 1 month.

The frequencies allocation of GSM communication in our country is GSM-900 (900 MHz) commonly. GSM-900 uses Tx = 890 - 915 MHz and Rx = 935 - 960 MHz .Tx means Transmission from mobile station to base Station and Rx means Receiving by mobile station from the base station.

Legal requirements for Walkie-talkie

Walkie-talkie and PTMR (Public Trunk Mobile Radio) have been developed for the purpose of military. In order to use these, we need a permit from a military officer that administers these kinds of telecommunication. Firstly, we need to submit a form to that officer by presenting what kind of organization uses Walkie-talkie with which purposes. Most of submissions will be allowed when submitted with exact evidences. When allowed, the officer will give a code number that is an available channel of frequency to use. Then we need to buy the required equipments for Walkie-talkie.

The frequencies allocation of Walkie-talkie may be increased according to user licenses. In our country, the frequencies allocation may between 300 kHz (minimum) and 300 MHz (maximum). Although there is an individual frequency for each organization or group of users, the users can use other available frequencies. But to be continuous communication with one organization of its own, user has to be at the frequency defined by this organization, base station.


Costs for GSM

The charges for GSM may include activation fees and advance deposit. Moreover, the equipments may also cost. The details of the charges and costs are being described in following table:


Cost (kyat)


Submitting Forms


Activation (License) Fees



GSM set x 1


80,000 - 900,000

Advance Deposit





The service charge is 50 kyat per minute for outgoing to both local and distance calls. For international call, the user may be charged 1.5 $ per minute. These charges will be deducted from the advance deposit and the MPT will send a message when the advance deposit is almost due.

Costs for Walkie-talkie

The Walkie-talkie is a free radio talk but it cannot be used by everyone. There is only need to get admission from military and buy some equipment to operate Walkie-talkie. The costs for buying equipments are as following:


Cost (kyat)


Submitting Forms


Base Station with Radio Tower



Walkie-talkie set x 1


60,000 - 300,000

Installation Fees




Other Accessories (extended antenna, headsets)




The service charge and tax are free because of using own antenna. However, the Walkie-talkie can be retreated by the military immediately.


Limitations of GSM

Frequency Overlapping (Interference)

If any place where there are a lot of Wi-Max and Wi-Fi internet zone, the GSM signal can be interrupted and even lost. Because they use frequencies that are almost same with frequency ranges of GSM.

Attenuation (Range)

Moreover, the clear voice and strengthen signal cannot get while inside the building and deep forest because of attenuation as signals have to pass many layers of walls and other interferences. And the further from the tower user is, the weaker the signal is.

Other Limitations

The other limitation is that the service charges for GSM communication. While using GSM, users are afraid of charges for long time phone's call. Moreover, the GSM will not work in the middle of a storm.

Limitations of Walkie-talkie

Frequency Overlapping

When different group of walkie-talkie users use same frequency band at the same time, there will be interruption between transmit/receive. Because walkie-talkie follows PTT (Push to Talk) procedure and it does not allow parallel transmitting i.e., two users who operate at same frequency cannot speak simultaneously. When speaking simultaneously, the voice received will not clear. So, the users within same groups have to operate by moving to another channel.

Frequency Interrupting

The Radio Frequency Interference (RFI) from certain applications such as AM and FM broadcast radio, cellular radio, Trunk Mobile Radio (TMR), and microwave radio can interrupt. But it can be avoided because the users can change or search the frequencies channel manually.


The range limitation of Walkie-talkie is actually based on the height of radio tower. As Walkie-talkie uses the lower frequency signals, they can expand widely because lower frequency signals can reproduce themselves.


By revising and comparing above two voice communications, Walkie-talkie (half duplex communication) is recommended to set up and operate for the two-way voice communications of Fire Department because of the following reasons.

Low price for Setting up and free for calling

The prices, was calculated at the Task-3 (3.3), for GSM is double expensive than Walkie-talkie. Moreover, the service charges (bill) are free for walkie-talkie. This can reduce other unnecessary costs for Fire Department.

Suitable for organization

As GSM is developed for purpose of personal use, it is not suitable for organization. If GSM is used in Fire Department, there may be personal use and the Department will be more charged for callings. But with Walkie-talkie, it is only to provide a radio tower. Moreover, as the range of the signals from base station (radio tower) can reach 40 km radius, it is enough for the area covered by the Fire Department.

More resistant from interferences

Sometimes, the communication can be delayed in GSM by interferences i.e. the user is not the service area. It can be avoided by using Walkie-talkie. If the standard frequency of the Fire department is interrupted, the base station will use the emergency channel to communicate firefighters even when they are out of office, in the department's vehicles.

Walkie-talkie can extend easily

When the department vehicles are so far away from the base radio station and in the highest interferences, the GSM may lose communication. But Walkie-talkie can solve this problem easily by using repeater. The repeater will receive the signals from base station and transmit again to Walkie-talkie sets. D:\KMD\IAD\Assignment\EN\Draft\Bar\reference.png

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Among many available telephone systems that can provide most appropriate features for business organizations, we would like to present and compare two telephone systems, KTS (key Telephone System) and PBX (Private Branch Exchanges).


The required equipments may only differ partially between two systems because each has same common features to be a multiline phone exchange system. The main basic equipments for these two systems are described as following.

Central Office Line

It means a central point for the termination of lines and trunks. Actually it is an integral part of the public switched telephone network. Many connections can be exchanged from those lines. Central Office Line may be 2 or more depending on the customers' needs. But 2 CO Lines is appropriate for small-sized organization like fire department.

Internal Switching Network

The Internal Switching Network is consisted of Main Switch and other related devices such as cards that facilitate phone operation. The Main Switch for KTS will different with one for PBX. In the PBX, the Main Switch will include microcontroller (or) microcomputer for control, data processing and logic. Logic cards, switching and power cards can be integrated to the PBX Main Switch to enhance the operation. However, most of the main switches that used in KTS are not programmable and customizable.

Telephone sets (or) Stations

The number of telephone sets depends on the number of users which are on the branched internal telephone lines. The type of stations may not be varied according to system used.

Interconnected Wiring

The interconnected Wiring includes from equipments needed for wiring to cables and sockets (connector).

Uninterruptible Power Supply (UPS)

Both systems require the Uninterruptible Power Supply which includes power switches, sensors and batteries to maintain power to Main Switch.


Features of KTS (Key Telephone Systems)

Hold: The Hold feature allows a user to temporarily suspend a call by depressing a designated hold button. When held, the user can answer another call. The first call lamp will flash to indicate the hold status. Then the user can retrieve the call by depressing the flashing line key. This process is known as recall, I-hold or exclusive hold.

Intercom: Another feature that included in KTS is Intercom (intercommunication system) in which talk paths are used exclusively from ordinary paths. This allows internal communications between stations belonging to a group or subgroup of privileged users.

Call Detail Recording (CDR): This feature provides information details on all incoming and outgoing calls for network usage reports. Information typically includes -

Originating and terminating station

Outgoing and incoming trunk

Time of connection

Elapsed time

Telephone number dialed

Features of PBX (Private Branch Exchanges)

Automatic Route Selection (ARS): This is an optional software feature and is also known as Least Cost Routing (LCR). This feature enables the user to program the system to route individual calls over the most appropriate selection carrier and service offerings.

Routing factors of ARS might depend on the Class of Service (CoS), or level of privilege, of the users.

Call Pick-up Groups: This feature enables users to answer calls for one another within the same workgroup. For this option, authorized users can invoke by entering a code on the set keypad or by depressing a designated feature button.

Call Forward: A call that will be transferred in the condition of a busy or no-answer condition can be defined an extension by a user. Moreover, this extension can be predefined.


Whatever the telephone system the Fire Department uses, the cost (primary or basic cost) for CO Line, Internal wiring, and Telephone sets will not different. The costs described in following table are based on the standard telephone system that is appropriate for single-site organization: fire department.

Basic Cost for Equipment

Equipment Name




CO Line




Telephone Sets + cable




RJ - 11 Connectors

~ 20



Crimper + Screw Driver




Total (Kyat)


Additional Cost of equipment required for KTS

For KTS telephone system, the additional cost for KTS Main Switch will be added to the basic cost.

Model Name




Transtel DK2 - 21


3 CO Line

8 analog ports

Caller ID

Auto attendant


Additional Cost of equipment required for PBX

The Main Switch for PBX will be more expansive than KTS and other related devices will be needed to enhance the system.

Model Name




Transtel LYNX


5 CO Line

12 analog ports

4 digital ports

Caller ID


Cost of Installation

When installing anyone of these systems, the estimated cost may depend on three main points. The following table shows the estimated cost for installing standard telephone system based on these 3 points.

The number CO Line in and braches lines out

The architecture of the building ,and

The customers' expectation.



Estimated Cost

2 CO Line in

1 line per 50,000


7 Internal Branches out

1 branch per 10,000


Wiring (170m)

1 m per 50


Total (Kyat)

~ 178,500

Total Cost

Phone System

Basic Cost

Additional Cost

Installing Cost

Total Cost

KTS System





PBX System






Telephone Bill

The unavoidable cost of operating any telephone is telephone bill. The Fire Department will cost telephone bill for all telephone branches according to the call durations multiplied by following charge rates that are classified by type.




Outgoing Local Call

1 Minute


Outgoing Distance Call

1 Minute


Outgoing International Call

1 Minute


We neglect telephone bills cost from total cost of operating because it depends on the call duration made.

Cost of operating the KTS Telephone System

There is only maintenance cost when operating KTS system. The telephone system that is applied is still needed to be maintained regularly since the system has been operating. The maintenance cost can vary according to the scope of maintain which are described as following table.



Unit Cost

Annual Cost

CO Line maintenance x 1

Twice a year



Telephone set maintenance x 1




Main Switch maintenance




Other accessories maintenance




Total Cost (kyat)


Cost of operating the PBX telephone system

When operating PBX telephone system, there will be cost for operator in addition to cost of KTS system. The operator is needed in PBX system because the operator will dial the internal telephone set number to connect line when the dialer does not know the desired dial number. The total cost of operating PBX system is described in following table.


Annual Cost

Total Operating Cost of KTS System


PBX Operator x 1 (35,000 monthly)


Total Cost (kyat)



By reviewing above information about two telephone systems, KTS and PBX, we recommend KTS (Key Telephone System) to be applied in Fire Department. We recommend KTS because of following reasons.

Organization Size

Key Telephone Systems are suitable for organization with 10 to 40 employees. At the Fire Department, there will not be users (or) employees more than 40. And then all of these employees may not always need to use the telephone.

KTS needs fewer budgets

As described above comparing prices, KTS will cost less than PBX. Although the KTS cost fewer budgets, it can provide all features that are essential for the Fire Department. Although PBX system offers a better long-term value, we need to consider Fire Department budget capabilities.

No need to wait for Emergency Calls

When dialer calls the Fire Department in fire emergency state, first dialer will meet the operator firstly in PBX. Then the dialer needs to dial number again to get access to chief or watch officer of the Fire Department. But in the KTS, the dialer can avoid those things. When dialing to the Fire Department, all telephones in the Fire Department will ring so they can have alert.

Simple To Upgrade

If the Fire Department would like to change the PBX (or) other systems while applying KTS, it is easy and incurs less expense. The KTS system is compatible with PBX or other systems. Besides, nowadays KTS system is capable to provide the features of PBX while still incurring less expense. So, we recommend KTS because of its cost-effectiveness.


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According to assignment, the measures that should put in place for Fire Department depend on these main two points:

What they need

In How situation

They need continuous electric power and communication line. There are many other ordinary ways i.e., generators using fuel, to resolve these problems. But if those serious events may take 1 or several months, these ordinary ways are not suitable because it is not easy to get the enough resources during like these situations. So, we have to use natural power to maintain operation of emergency devices uninterruptedly.


We would set up solar plate at the Fire Department to get electrical power from solar energy. With this solar energy, we can recharge the batteries by battery charger. We will need a large area of solar plate as we need the enough power to operate the whole Fire Department well. Moreover large area of solar plate, we also need multiple high voltage batteries such as 12 V or 24 V because one 24 V battery cannot serve power all night. D:\SETUP\Windows Desktop Decoration\Icons Selection\PNG\5.png

With the batteries that recharged at day, we can maintain our Fire Department's operational as well as at night. We would use inverter to reuse power from batteries for lighting, recharging other devices and other operations.

We also need emergency light that can be automatically recharged by hand pressing or squeezing. The power from batteries is enough for lighting and recharging but we should not use until the batteries power is empty. Because we cannot know tomorrow will be sunny or cloudy.

Set up solar energy

Battery charger



Emergency light (rechargeable by hand shaking)


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If we can put enough power to Fire Department, the communication can also serve well because all communication devices use electric power AC or DC. For incoming communication, we would put FM radio sets that use AA sized rechargeable batteries. The Fire Department can get information continuously about the situation from outside.

For both incoming and outgoing communication, we would Fire Department to set up Satellite telephone line. So, the Fire Department can maintain communication with the outside world or other departments. And then we would like to put the charger that can recharge by hand pressing. By using this, Fire Department remains communicated even if the solar energy is out.

Set up Satellite telephone line

Satellite telephone handsets

FM radio sets

Battery charger (chargeable by hand pressing)

Li-ion Battery


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After putting emergency devices and solar energy operation, we would like to pay training to Fire Department about how to use and repair these things. Besides well using these devices, all officers in Fire Department should know how to repair. If so, Fire Department can continue operations in the events of serious even if any of hardware or devices is failure.

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The any network applied should be cost effective, long termed and at the least troubleshooting. Besides computer network, telecommunication network also should be fault-tolerance and can operate at any situation. By following to these facts, we have been established the network of the Fire Department.

In the Task -1, while creating in-house network (LAN) with Star topology and wireless medium provides the network with greatest advantages that individual devices can connect the node and least troubleshooting.

Moreover in task 2, by installing an internet line with optimal speed, the whole computers connected with LAN in department can easily use the internet services. With the star topology, the head of department can get the centralized management on these services.

Also in telecommunication network (Task 3), Walkie-talkie is fault tolerance and can service although in extreme storm. Then, users can adjust the frequencies manually. Great advantages are walkie-talkie cannot be interfered and extended easily by using additional receivers in fire engines.

For the telephone system (Task 4), KTS (Key Telephone System) is cost effective because it can be installed with low cost while still providing PBX features. Besides these, it can be easily upgraded to PBX or other hybrid telephone with few additional installations.

In Task 5, Satellite Phone, FM radio with Solar Energy is most suitable for incoming and outgoing communication with continuous power supply in the event of a serious incident such as war.


We cannot estimate the cost for Local Area Network because we don't know the number of Computers involved in this LAN.

Operation Name


Local Area Network


Internet Connection

~ 2,000,000

Voice Communication (Walkie-talkie)


Telephone System (KTS)


Measures put in serious incident

~ 3,500,000

Overall Cost

~ 9,048,500


Finally, however we use the latest and effective technologies in applying these networks if users don't know all of their features, they cannot be operated in full efficiency. So, after establishing a new system, the Training should be first taken. Moreover, users should be enabling to make self-repair when hardware or software is broken. If do so, the Fire Department can cover the unnecessary services cost from companies.


The system applied to the Fire Department may be needed to take maintenance, update and upgrade when necessary. If we cannot effort to maintain, update and upgrade to these applied networks and systems, they cannot provide the needs of Fire Department anymore for further future. So, the following facts should be carefully taken.


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Electrical devices should be placed free from moisture.

These devices should be used for office purpose

Should be unplugged the power when unused

Should take regularly check on emergency devices


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Updating antivirus software when using internet

Application programs should be regularly updated

Should be take regular training for users


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Hardware devices should be upgraded when they have not enough to full fill the requirements of Fire Department