Network media

Published: Last Edited:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.


My name is May Thwe Aye. I am attending now International Advanced Diploma in Computer Studies (IADCS) from Myanma Computer Company Limited (MCC) head office at Yangon. We have to learn four core subjects and three elective subjects including the assignments and a project in this class. But we are learned one elective subject and two core subject including the assignments in first module.

Now I am doing Enterprise Networking assignment. This title is "Police Department". This assignment is really given me so many knowledge and experience.


Initially, I would like to thank my parents to express my deep gratitude for their help and all kinds of support throughout our assignment period. And then, I am very grateful to Lecturer U Aung Thu Thu (who teaches us Enterprise Networking). Our course manager, Daw Aung Thandar Linn Myint, is also an unforgotten person to be grateful.



Network topology recognizes five basic topologies:

§ Bus topology

§ Ring topology

§ Star topology

§ Tree topology

§ Mesh topology


Bus topology is a simple topologies to install, does not require a lot of cable. There are two most popular types of Ethernet-cable, which are used in this topology are 10Base-2 and 10BaseT. Bus topology networks working with very limited devices. It performs well as long as the computer count to stay in the 12 - 15, the problem arises when the number of computers increases. Bus topology uses a common cable (backbone) to connect all devices in the network in a linear form. Network adapters all network devices attached to a cable based communication medium. When any computer sends a message to the network, it is transmitted across the network, but designed computer receives the message and process it. Bus topology provides ease-of-network, but there is a big drawback of this topology, if one of the major cable networks will be damaged, it will be closed throughout the network.


The ring topology is one of the old ways of building design computer networks, and it is largely outdated. FDDI, SONET, or Token Ring technology used to create a ring technology. It is not widely popular in terms of usability. In the ring network, every device has exactly two neighbors for communication purposes. All messages pass through the rings in their same directory, either clockwise or counterclockwise. In the event of failure of any device or cable, the whole network is down and communication is impossible.


In local networks, where a star topology is used, each machine is connected to a central hub. In contrast to the bus topology, star topology allows each machine on the network as a point to point connection to the central node. All traffic that crosses the network passes through a central hub. The Center acts as a signal amplifier or repeater which in turn gives a signal to travel long distances. As a result, each machine is directly connected to a hub; star topology is the simplest topology for the design and implementation. This topology is easy to add other machines. If the hub fails the whole network will not as a result of this center being connected to each machine on the network.


A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable. Tree topologies opportunity to expand the existing network. It supports for multiple hardware and software vendors. If the backbone line breaks, the entire segment goes down and more difficult to configure and wire than other topologies.


In a mesh network whose nodes are all connected to each other in a fully connected network. The network can act as an independent router, regardless of whether connected to another network or not. This allows continuous communication and reconfiguration around broken or blocked the path to the "hopping" from node to node until they reach the goal. Mesh network with redundant links is an example of redundant topology. The level of redundancy can be measured by network connectivity.


Network media is the actual path travels as it moves from one component to another. Common types of media for LANs are:

§ Copper cable (UTP, STP)

§ Fibre optic cable

§ Radio transmission

Advantages of UTP

§ UTP, twisted pair is good enough for large data applications, but only up to 100 Mbit / sec, and the fiber goes to a few gigabytes. Fiber is more, if you need it.

§ UTP is cheap and very easy to use, while the fiber path, difficult to handle, and you need to do is round the corners.

§ UTP can be cut with a knife and crimp on the connector is easy, but with a layer, you need special tools and skills to stop them.

§ Finally, you need power and LEDs deliver electrical signals to fiber, and photodiode with the amplifier power to get signals from the other end.

§ In general, fiber optical cable is a great performer, wonderful, and the best thing ever IF YOU NEED THAT MUCH BANDWIDTH. But for most applications UTP is plenty good enough.

§ If you need fiber, the plastic is easier to use for short runs, while the glass has higher performance and more difficult to work with.

Disadvantages of UTP

§ Twisted pair to electromagnetic interference greatly depends on the pair twisting schemes (usually proprietary producers) remain intact during the installation. As a result, twisted pair, as a rule, stringent requirements for maximum traction tension, as well as minimum bend radius. This relative fragility of twisted pair makes the installation practices an important element in the enforcement of the cable

Advantages of Fibre optic cable

§ Fibre optic cables have a much greater bandwidth than metal cables.

§ Fibre optic cable is less susceptible to signal degradation than copper wire.

§ Fibre optic cables weigh less than a copper wire cable.

§ Data can be transmitted digitally.

§ Lower-power transmitters can be used instead of the high-voltage electrical transmitters used for copper wires.

§ Unlike electrical signals in copper wires, light signals from one fibre do not interfere with those of other fibres in the same cable.

§ Because no electricity is passed through optical cable it is non-flammable, and immune to lightning.

§ Impossible to tap into a fibre optics cable, making it more secure

Disadvantages of Fibre optic cable

§ Fibre optic is that the cables are expensive to install.

§ The termination of a fibre optics cable is complex and requires special tools.

§ They are more fragile than coaxial cable.

Advantages of radio transmission

§ It is not required cable.

§ It is easy to use.

§ It is portable.

§ In short time, can give the information to the police cars

§ All the messages given out by the radio station are heard on each of the radio-equipped cars.

Disadvantage of radio transmission

§ It is not safety.

§ Police Department must own and operates a radio transmitting station.

§ Requires of its cars equipped with receiving sets.



A local area network (LAN) provisions networking capability to a group of computers in immediacy to each other such as in an office building, a school, or a home. A LAN in turn often connects to other LANs and to the Internet or other WAN.

Our police network to use the Star topology because this topology is the best communication method of our system network. We want to connect to computers with copper cable. We recommend radio transmission for orders to a police car to the scene of a crime, fire or accident.


(a)Internet Service that may required in police department


Voice over Internet Protocol (VoIP) is a general term for a family of transfer of technology to provide voice communication over networks IP, such as the Internet and other packet switched networks. Other terms are often synonymous with VoIP are IP-telephony, Internet telephony, voice over broadband (VoBB), broadband telephony and broadband phone.

Internet telephony refers to communication services - voice, facsimile and / or voice messaging applications - which are transported through the Internet, rather than the public switched telephone network (PSTN). VoIP systems use protocols to control your session setup and tear down calls, as well as audio codecs, which encode speech enable communication via IP, digital audio through the audio stream. Codec usage varies between different implementations of VoIP (and often a number of codecs used), some implementations rely on narrowband and voice compression, while others support the stereo codec high accuracy.


File Transfer Protocol (FTP), is a standard network protocol used for exchanging and manipulating files over TCP / IP networks, such as the Internet. FTP is based on a client-server architecture and uses a separate control and data transfer between client and server applications. FTP is also frequently used as a component of an application for automatic file transfer program for internal functions. FTP can be used with user-based authentication password or the anonymous user access. Trivial File Transfer Protocol (TFTP) is similar, but simplified, inconsistent, and not an authorized version of FTP.


Hypertext Transfer Protocol Secure (HTTPS) is a combination of Hypertext Transfer Protocol with SSL / TLS protocol to provide encryption and secure identification on the server. HTTPS connections are often used for payment transactions at the World Wide Web and for sensitive transactions with corporate information systems. HTTPS should not be confused with the Secure HTTP (S-HTTP), specified in RFC 2660.


Internet Protocol Security (IPSec) is a set of protocols for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet in the data stream. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and discussion of cryptographic keys, which will be used during the session. IPsec can be used to protect the data flows between a pair of hosts (for example, users of computers or servers), between a pair of security gateways (eg routers or firewalls), or between a security gateway and a host.

IPsec is a dual mode, from end to end security scheme operating in the Internet layer in the protocol stack of the OSI model or 3rd level. IPsec is the successor to the ISO Network Layer Security Protocol (NLSP). IPsec officially listed in the Internet Engineering Task Force (IETF) in Request for Comments series discusses the various components and extensions, including the official style of capitalization of the term.


The webcam is a video capture device connected to a computer or computer network, often using the USB port or if it is connected to an Ethernet or Wi-Fi.

The most popular is the use of video-telephony, which allows the computer to act as a videophone or video-conferencing station. It can be used in Messenger programs such as Windows Live Messenger, Skype and services, Yahoo Messenger. Other popular use, which include video recording files, or even images that are available through numerous software programs, applications and devices.

Webcams are known for low manufacturing costs and flexibility, making them the lowest cost form of video telephony.

The term "webcam" can also be used in its original sense, camcorder connected to the web continuously for an indefinite time, but not for a particular session, as a rule, in order to provide for all visitors to its web page. Some of them, such as those used as an online traffic cameras, are expensive, reliable, professional video cameras.

(b)The connection speed

The connection speeds of E-mail will adequate 64 kbps and 256 kbps is preferable. FTP is sufficient 128 kbps and 1 Mbps is preferable. VoIP is enough 64 kbps for normal conversation and 512 kbps is preferable for peak hours.

(c)Internet Service Providers that can meet in our country

(d) Recommendation

Our country has two ISP Services these are Myanmar Post and Tele-communication (MPT) and Bagan Cyber Tech. These two providers are distributing to the internet service of our country. I want to suggest that WiMAX technology is the best way of solving the police department. Because the data transfer rate of this technology is too large and the connection speed is very strong.


Task 3 (a)

GSM (Global System for Mobile communications)

GSM (Global System for Mobile communications: originally from Special Mobile Group) is the most popular standard for mobile phones in the world. His promoter, GSM Association, estimates that 80% of the global mobile market uses the standard. GSM is used by more than 3 billion people in more than 212 countries and territories. His widespread international roaming gives you a very common between mobile operators, allowing subscribers to use their phones in many parts of the world. GSM differs from its predecessors by the fact that both signaling and speech channels of digital and, therefore, considered the second generation (2G) mobile phone system. This also means that data communication was easy to build into the system. GSM EDGE is a 3G-version of the protocol.

The structure of a GSM network

The ubiquity of the GSM was the advantage of both consumers (who benefit from the ability to move and switch carriers without switching phones) and network operators (who can choose equipment in any of the many vendors implementing GSM). GSM is also the first low-cost (to the network carrier) alternative to voice calls, short message service (SMS, also called "text messaging"), which is now supported on other mobile standards as well. Another advantage is that the standard includes the world's number one emergency telephone; 112.This facilitates international travel to connect to emergency services, not knowing the local emergency number. Newer versions of the standard were backward-compatible with the original GSM phones. For example, Release '97 of the standard added packet data capabilities, by means of General Packet Radio Service (GPRS). Release '99 introduced higher speed data transmission using Enhanced Data Rates for GSM Evolution (EDGE).


Walkie-Talkie (more formally known as the portable transceiver) is a manual, portable, two-way radio. Its development during the Second World War in different ways, credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineers at Motorola. Similar projects have been created for other armed forces, and after the war, walkie-talkies spread to public safety and eventually commercial site work. Key features include half-duplex channel (only one radio transmits at a time, although any number can listen) and Push-To-Talk (PTT) to start the transfer. A typical walkie-talkies like the telephone, perhaps a little more, but still a single unit, with an antenna protruding from the top. Where a phone's earpiece is only loud enough to be heard by the user, a walkie-talkie's built-in speaker can be heard by the user and those in the user's immediate vicinity. Hand-held transceivers may be used to communicate with each other, or vehicle-mounted or base stations.

Some cell phone networks offer push-to-talk phone, which allows Walkie-Talkie-like operation over the cellular network without dialing the call every time.

Radios for public safety, commercial and industrial purposes, may be part of the trunk radio systems, which dynamically allocate radio channels for more efficient use of limited radio frequency spectrum. Such systems are always working with a base station that acts as a repeater and controller, although some phones and mobile phones may have a mode, bypassing the base station.

(b)Legal requirements for operating the system in our country

There are two basic formats for the two-way radios. They are ultra high frequency (UHF) radio and very high frequency (UHF) radio. No bandwidth is inherently better than others. Each has its pluses and minuses. Both formats are an effective way to communicate with another person, such a decision on the right radio for you depends on your application.

Two radios communicate with each other through the use of radio waves. Radio waves have different frequencies, and tuning the receiver to a specific frequency you can choose a specific signal.

Radio waves are transmitted as a series of cycles, one after another. You will always see "The abbreviation Hz is used to indicate the frequency of the radio. Hertz equals one cycle per second.

Radio waves are measured by kilohertz (kHz), which is equal to 1000 cycles per second, or megahertz (MHz), which is equal to 1,000,000 cycles per second--or 1000 kHz. The relationship between these units is like this: 1,000,000 Hertz = 1000 kilohertz = 1 megahertz. You may also hear the term "wavelength" when you hear about radio waves.

This term in the early days of radio frequencies, when measured in terms of the distance between the peaks of two consecutive cycles of radio waves instead of the number of cycles per second. Lower frequencies produce a longer wavelength. While wavelength measures distance between the peaks of cycles, frequency refers to how long the measured time is between the "crest" and "trough" of a wave arriving at the source. So frequency measures time instead of distance, but they are essentially both saying the same thing.

What is significant about wavelength for two-way radios is that it affects transmission range under certain conditions. A longer wavelength as a general rule lets a radio signal travel a greater distance. Lower frequencies or wavelengths have greater penetrating power. That's one of the reasons they are used for communicating with submarines. VLF radio waves (3-30 kHz) can penetrate seawater to a depth of approximately 20 meters.

So a submarine at shallow depth can use these frequencies. So from what you read above you may think VHF is always the better choice for a two-way radio no matter where you are using it. That's not necessarily true.

Even though VHF has better penetrating capabilities, that doesn't necessarily make it the better choice for buildings. Remember the conversation about wavelength above? Wavelength has a big impact on transmission.

FCC Licensing

If you are purchasing a radio for your business, most business-band radios require you to get a License from the FCC before you can use the radios. One exception to this is if you purchase adios that operating in the MURS frequencies.

For other licensing questions, you can call the FCC Consumer Center at (888) 225-5322. Below is the FCC's licensing process with links to their website:

§ Gathering Information

§ Frequency Coordination

§ Filing Your Application

§ Immediate Operation

§ Notification of Construction

§ Renewal of License

(c) Set up cost of the police department

(d) Limitations

If you go down to your local building supply or discount store you will see radios that say they have a range of 14 miles, 22 miles, or something like that. Yet when you take them home you find that they don't even go a mile.

One of the biggest factors to reducing range is the obstacles in the path of transmission. These obstacles absorb and reflect the radio waves so while a radio advertised to go 22 miles may actually do that if both users are standing on peaks of a mountain with nothing in between, the same radio can't go a half mile through a forest. Two-way radios communicate "line of sight," which means that if you can see between two points, the radio should be able to communicate between these two points. Consider that the radio the Apollo astronauts on the moon used to communicate only used one watt of power and you'll get the picture on this.

If you consider that two points on land or water become invisible after about five miles between them because of the curvature of the Earth, you can understand that communicating more than five miles becomes difficult even if there are no obstacles between the radios. The key to getting more range is either to raise the height of the antenna, increase the power of the radio, or both.

Government radio stations often rated power output, consumer radios are often controversial and evaluated a mile or kilometer count, because in direct line of sight distribution of HDTV signals. Walkie-Talkie traffic in the area of 27 MHz and 400-500 MHz UHF spectrum, there are units that use 49 MHz (shared with cordless phones, baby monitors and similar devices). Spread-spectrum scheme is used in eXRS station allows up to 10 million virtual "channels" and provides a link between private two or more units.

(e) Recommendation

In task 3, I have investigated about the two way voice communication method, data transmission methods, accuracy of the voice communication, additional services and limitations. The categories include Global System of Mobile (GSM) and walkie-talkie. The devices and technologies can use communication of police department. Walkie-talkie is to use the voice communication with third party or communicate with each other.

Personal two-way radios are also sometimes combined with other electronic devices; Garmin's Rino series combine a GPS receiver in the same package as an FRS/GMRS walkie-talkie (allowing Rino users to transmit digital location data to each other) Some personal radios also include receivers for AM and FM broadcast radio and, where applicable, NOAA Weather Radio and similar systems broadcasting on the same frequencies. Some designs also allow the sending of text messages and pictures between similarly equipped units.

The two-way walkie-talkies rage is very excellent and this range is so far so good. The area range spectrum is very long distance. The ranges of these devices have a range of 14 miles, 22 miles, or something like that.

The frequency of Radio waves are measured by kilohertz (kHz), which is equal to 1000 cycles per second, or megahertz (MHz), which is equal to 1,000,000 cycles per second--or 1000 kHz. The relationship between these units is like this: 1,000,000 Hertz = 1000 kilohertz = 1 megahertz. You may also hear the term "wavelength" when you hear about radio waves.


Task 4 (a)

Private branch exchange (PBX) is a telephone exchange that serves a particular business or office, and not one that the common carrier or telephone company operates for many businesses or for the general public. PBXs make connections between internal telephones private organizations - usually a business - as well as connect them to the public switched telephone network (PSTN) via trunk lines. Because they include telephones, fax machines, modems, and more general term "extension" is used to denote any end point on the branch.

PBXs are differentiated from "key systems" in that users of key systems manually select their own outgoing lines, while PBXs select the outgoing line automatically. Hybrid systems combine features of both.

Initially, the main advantage of PBXs was to save on internal phone calls: handling circuit switching locally reduced charges for local telephone services. As ATS gained popularity, they began to offer services that were not available in the networks of operators, such as hunt groups, call forwarding, and extension dialing. In 1960, ATC simulation known as Centrex provided similar features from the central telephone exchange.

Two significant developments during the 1990's led to the emergence of new types of PBX systems. One of them is the massive growth of data networks and increased public understanding of packet switching. Companies need to packet switched networks for data, so using them for telephone calls was tempting, and the availability of the Internet as a global delivery system made packet switched communications even more attractive. These factors have led to the development of VoIP PBX. (Technically, nothing was time "exchanged" anymore, but the acronym PBX was so widely known that he is still used.)

Another trend was the idea of core competence. PBX services had always been difficult to arrange for small companies, and many companies realized that the consideration of their own telephony was not their core competency. These considerations led the concept of Hosted PBX. In the Install Hosted PBX is a telephone and managed services, as well as opportunities and challenges delivered via the Internet. The customer simply subscribes to a service, rather than buying and maintaining expensive equipment. In essence, it removes the branch from the private premises, moving it to a central location.

Task 4 (b)

Menu Options / IVR, Multiple Extensions, Unlimited Simultaneous Calls, Conferencing, Time Conditions, Call Queuing, Informational Lines, Low International Rates, Portability, Internet Dependent, and Multiple phone Numbers are available in virtual PBX system.

Functionally, the PBX performs four main call processing duties:

§ Establishing connections (circuits) between the telephone sets of two users (e.g. mapping a dialled number to a physical phone, ensuring the phone isn't already busy)

§ Maintaining such connections as long as users require them (i.e. channelling voice signals between the users)

§ Disconnecting those connections as per the user's requirement

§ Providing information for accounting purposes (e.g. metering calls)

In addition to these basic PBX functions offer many other calling features and capabilities, with different manufacturers providing different functions in an attempt to differentiate their products. Common capabilities include (manufacturers may have a different name for each capability):

§ Auto attendant

§ Auto dialing

§ Automatic call distributor

§ Automated directory services (where callers can be routed to a given employee by keying or speaking the letters of the employee's name)

§ Automatic ring back

§ Call accounting

§ Call Blocking

§ Call forwarding on busy or absence

§ Call park

§ Call pick-up

§ Call transfer

§ Call waiting

§ Camp-on

§ Conference call

§ Custom greetings

§ Customised Abbreviated dialing (Speed Dialing)

§ Busy Override

§ Direct Inward Dialing

§ Direct Inward System Access (DISA) (the ability to access internal features from an outside telephone line)

§ Do not disturb (DND)

§ Follow-me, also known as find-me: Determines the routing of incoming calls. The exchange is configured with a list of numbers for a person. When a call is received for that person, the exchange routes it to each number on the list in turn until either the call is answered or the list is exhausted (at which point the call may be routed to a voice mail system).

§ Interactive voice response

§ Music on hold

§ Night service

§ Shared message boxes (where a department can have a shared voicemail box)

§ Voice mail

§ Voice message broadcasting

§ Voice paging (PA system)

§ Welcome Message

Task 4 (c)

VoSKY Exchange 9140 PBX-to-Skype Gateway

§ Lines to the office PBX without changes to existing PBX or phone equipment.

§ calls without any changes to existing PBX equipment, phones or user PCs

VoSKY Exchange 9140 PBX-to-Skype Gateway

Steren 310-368 50 Pair 110 Type Modular 66-IDC Wiring Phone PBX

Used in equipment rooms and wiring closets to connect telephone systems PBX systems and other low-speed terminal equipment. Specifications: 50-Pair Modular.

Steren 310-368 50 Pair 110 Type Modular 66-IDC Wiring Phone PBX ...

Premier 1224/2460 Phone System Chassis PBX Telephone

Premier 1224/2460 Phone System Chassis PBX Telephone Includes wires and some mounting equipment.

Premier 1224/2460 Phone System Chassis PBX Telephone

Linksys SPA942 VoIP telephone

Stylish and functional in design, the Linksys SPA942 VoIP telephone is ideal for a residence or business using a hosted IP telephony service, an IP PBX, or a large scale IP Centrex deployment.

Cisco 7940 IP Phone

The Cisco 7940 works extremely well with Asterisk - Trixbox - and FreePBX systems. Direct access to voice mail.The Cisco IP Phone 7940G identifies incoming messages and categorizes them for users on the screen. Local and Personal Directories allow for quick number lookup.No system administration is required.

Aastra 57i IP Phone (6757I)

Aastra 57i IP Phone. (6757I) The 57i from Aastra offers powerful features and flexibility in a standards based, carrier-grade advanced level expandable IP telephone. With a sleek and elegant design, large 144 x 128 pixel graphical backlit LCD display and 6 dynamic context-sensitive softkeys, the 57i is fully interoperable with leading IP.

Aastra 57i IP Phone (6757I) - Click Image to Close

Task 4 (d)

Some cell phone networks offer push-to-talk phone, which allows Walkie-Talkie-like operation over the cellular network without dialing the call every time.

Radios for public safety, commercial and industrial purposes, may be part of the trunk radio systems, which dynamically allocate radio channels for more efficient use of limited radio frequency spectrum. Such systems are always working with a base station that acts as a repeater and controller, although some phones and mobile phones may have a mode, bypassing the base station.

There are various accessories available for walkie talkies such as rechargeable batteries, drop in rechargers, multi-unit rechargers for charging as many as six units at a time, and an audio accessory jack that can be used for headsets or speaker microphones.

When using a headset with voice activation (VOX) to the user can talk with hands free. Several types of audio accessories available such as Speaker microphones that clip around the ear type of security with ear pendant Push-To-talk switch and built-in microphone, headset, which has a switch Push-to-talk earbuds, which looks more like what you will find on the music player, or one ear for easy-head headset with microphone boom and pendant Push-To-switch say they were similar center agent phone calls. Above costs are the costs to the system.

Task 4 (e)


The recommendation for the Task 4 is the PBX telephone system to be used. This telephone system to be used in my police office because this function is achieve, the PBX performs four main call processing duties:

§ Establishing connections (circuits) between the telephone sets of two users (e.g. mapping a dialed number to a physical phone, ensuring the phone isn't already busy)

§ Maintaining such connections as long as the users require them (i.e. channeling voice signals between the users)

§ Disconnecting those connections as per the user's requirement

§ Providing information for accounting purposes (e.g. metering calls)

In task 4, I have investigated about the telephone system, additional services and limitations. The categories include PBX (Public Branch Exchange) and KTS(Key Telephone System). The PBX system to use the wide range communication serves are available to our police department. Our police department require the wide range communication services and to solve the criminal case of our country. The PBX system is more comfortable than KTS service, because the PBX system to apply the IP with communicate to each other. Thus why, I was suggested that IP PBX system is the best solution of our police department.


The police office department in Townsville has been restructured and is shortly opening a new headquarters building. The building will house all the communication and computer system for the police department.

Townsville Police Department covers an area of 100 square kilometers and has a chief Constable who is responsible for the policing of that area.

I have constructed the POLICE Department with Global Positioning System (GPS), General Packet Radio Service (GPRS), Global System of Mobile (GSM) and Geographical Information System (GIS).

In task 1, I have taken the research for the police department paying attention to the two way voice communication method, the accuracy of the data transmission method, the information delivered by the head office to the branch, the method of data transmission from vehicle to centre, the cost per device of using the system, Additional services that the system can provide and limitations of the system. And then to select the topology of network communication, decide which topology to make better than to our police department. The recommendation for task 1 is already shown at the end of task 1.

In task 2, I have investigated the methods of communication service and to select the one is the best and compare the price and services. Which services are meet with our police department and recommendation for task 2 is already shown at the end of task 2.

In task 3, I have investigated the more detail of two way voice communication method. To find the GSM, walkie-talkie system function and frequencies band width of the each system. The cost per device and which device can use, these devices to implement our police department. The recommendation for task 3 is already shown at the end of task 3.

In task 4, I have investigated the telephone system available of our country for single-site organizations. The police department which telecommunication system to use and I was suggested PBX and KTS system to use our police department. This telecommunication system is the best of our police department. The recommendation for task 4 is already shown at the end of task 4.