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computer fundamental and networking

Published on March 2017 | Categories: Documents | Downloads: 4 | Comments: 0



What is computer network?
Two or more than two computer systems connected through a communication medium like cables are termed (define) as a Network. Computer Network is a communication system, which links computers and their resources.(deceives) Computer Resources are storage devices e.g. Hard disk, tape drive, CDROM, MODEM, printer, etc and any other computing system (Mainframe, Minicomputer etc.).

BENEFITS (advantages) OF A computer NETWORK?
Following are the benefits of a networking which help to increase the productivity: Information Sharing Printer Sharing ( one printer can be used bye the all the department of the company) Hard Disk Sharing ( one storage devices can be used by the all the company) Modem Sharing ( internet can be used by one modem by all the labs in the school) Hardware Sharing ( Software Sharing Service Access Easy Back-Up Management Security Centralized Administration and Support

LAN connects computers that are located near each other or at the same location.

A corporate network ( any company or organization) consisting of several building in a campus an example of a LAN

y y y y

Physical Distance Between the computers will be around 100 meters It covers a relatively small area, such as a building, home or an office Used to share printers, files and other resources over the LAN. Example: School Lab

WAN connects a numbers of computers which are located at a greater distance from one other or at different location. Internet is an example of WAN

Wide Area Network (WAN) Physical Distance Between the computers will range from 10 Kilometers and Above It covers a relatively large area, such as a offices from country to another country Used to share printers, files and other resources over the Network.

Example: Banks in India, Internet, Sutherland,USA, CANADA, INDIA offices

MAN (Metropolitan Area Networks
Networks that share some of the characteristics of both LANs and WANs are sometimes referred to as Metropolitan Area Networks (MAN). The MANs usually cover a wider geographic area than LANs. The main objective of MANs is to interconnect LANs located in a entire city or metropolitan area.

Physical Distance Between the computers will range from 100 meters to 10 Kilometers. It covers a relatively large area ,such as a offices from one place to other place in the same city or to connect near by building Used to share printers ,files and other resources over the Network. Example : University Labs,

Characteristics or Difference between the types of network? Or Difference between the LAN, WAN, MAN?
The key characteristics, which are often used to differentiate between these two types of networks, are as follows: Geographic Distribution ( where the computer are?) Data Rate (speed) Error Rate Communication Link ( how many lines are there ? speed of tem? Ownership Communication Cost

Classification of Networks (Based on Grouping

Peer to Peer Network
Each computer is attached to the network in a ring or bus fashion and is equal to the other units on the network. This network is useful if we have a small network and there is no need for managing or security. It can also be defined as Collection of computers interconnected together to share information and resources without any administration. y

Client / Server Network

In this dependent workstations, referred to as clients, operate in conjunction with a dedicated master computer called a server. Client request the server and sever serves the client if the client has permission to access what it requested. This type of network is need in case we need management and security , Example :Office computers in different departments. There are two types of administration: Centralized Administration : One system controls all the other systems. Distributed or Decentralized Administration:Administration is done from multiple

It refers to the physical layout of the network, especially the location of the computers and how the cable is run between them. The choice of the networks topology for installing a computer network depends upon a combination of factors, such as: The desired performance of the system. ( decides ) The desired reliability of the system. it will decides Size of the system.. (how many number of the devices can be connected ) Expandability of the system. Availability of communication lines. (more line more speed) Delays involved in routing information from one node to another.( effects decrease in speed)

Types of network TOPOLOGY? Classification of network topology? Explain network topology ?
1. Bus type network 2. Ring type network 3. Star type network


The bus topology refers to a linear arrangement of computers In Bus topology the computers are connected serially. that are connected together by a single cable referred to as the trunk or backbone. It is often used small, simple or temporary.  when a network installation is small,  when a network installation is simple  When a network installation is temporary. Advantages: it is Simple, it is Reliable, it is Easy to use And it is easy understood. Easy to install Data travels to all the system before it reaches destination node Least (small) amount of cable to connect computers. Less number of lines will be connected to computer. Easy to extend a bus with the help of a repeater. Easy to join more computer.


A star network consists of one central switch, hub or computer which acts as a router to transmit messages. In star topology all the computers are connected to a central place called HUB/Switch.

Advantages: It has Good Performance Easy to install Time taken for data transfer between systems are same. It is Easy to set up and to expand. More computers can be joined easily. Any non-centralized failure will have very little effect on the network, Whereas on a ring network it would all fail with one fault. One failure will effect to whole network. Disadvantages: Expensive to install cost will be more

Extra hardware required to connect more computer more numbered devices will be required If the host computer fails the entire system is affected.

A ring network is a topology of computer networks where each connected to node is two other nodes, so as to create a ring. All computers are connected in ring type.

Advantages: Data is quickly transferred without a bottle neck . ( data rate will be same for all computers) it is very fast, all data traffic is in the same direction The transmission of data is simple as packets travel in one direction only. Adding additional nodes has very little impact on bandwidth. More number of the computer can be joined without change in data rate. It prevents network collisions because of the media access method or architecture required. ( two or more computer will fight for the same number of data)

Disadvantages: Data packets must pass through every computer between the senders and recipient therefore this makes it slower. Slower speed.

If any of the nodes fail then the ring is broken and data cannot be transmitted successfully. ( failing of any node or line will effect the whole network) It is difficult to troubleshoot the ring. ( difficult to find fault) Because all stations are wired together, to add a station you must shut down the network temporarily. In order for all computers to communicate with each other, all computers must be turned on. ( all computer must be connected for successful running of the all network)

Mesh Topology
In Mesh topology all the computers are connected to each others using separate cables

Characteristics advantage disadvantage of the mesh topology All system can communicate with each other It is more Costly Large number of the cables are required If particular cable fails the systems connected by those cable alone will not able to communicate between themselves but they can communicate with all other systems.
What is Computer? What are the advantages and disadvantages of computer?

Computer is an electronic device. It accepts raw data as well as instructions from the user, process it and gives meaningful information as required by user as per given instruction.

Advantages: (a) Computer works very fast. (b) Computer gives accurate result. (c) It can process millions of instructions per second. (d) Computer is very versatile. (e) Computer works at constant efficiency. (f) Perform repetitive tasks very well without error. (g) Computer can store information for future retrieval or use. (h) Computer can communicate with other computer systems.

Disadvantages: (a) If wrong programmed then it produces wrong answers. (b) If it gets down then so many working hours wasted. (c) It brings unemployment because one computer can handle work of many people. (d) Stealing of information through computer is become too much easy. (e) Computer on Internet is not safe due to Virus or other attacks.

1. What is a Computer? Computer system is defined as information processing machine use to do arithmetic and logical operation with capacity to store data temporarily and or permanently. A computer can store, process, and retrieve data as and when desired.

Block diagram of computer system

Definition: - a computer is an electronic device which takes data and instructions from the user and after processing producing gives result in useful form. During processing it has to perform:Taking data and instruction from user. Conversion data into information. Give/display the result.

Component of computer
A computer system of four units(1) Input unit (2) Output unit (3) Control processing unit (4) Secondary storage unit.

(1) Input unit Data and instruction must enter in to the the computer system before any computation can be performed. This task is performed by the input unit.

It needs the instruction and data. Its convert these data and instruction in computer expectable. Its supplied the converted instruction and data to the computer system for processing. (2) Output unitThe job of an output unit is just refers to input. It sands the information from the processing to the user. Computer works with binary number. Out put devices will convert it in to the see able form. (3) Control processing unit- the memory unit, control unit, arithmetic and logical unit to a computer are jointly known as control processing unit. The C.P.U is the brain of computer. In a human body are function directed by the brain. Similarly in a computer system in a computer system all major calculation is made

inside the C.P.U.
(4) Memory unit (primary memory or secondary) memory unit of C.P.U is also known as primary memory unit. Primary memory unit is used to store data and instruction result. This information is stored temporary. This storage can how information only which the computer is an as such as the computer switch off the data get erased. (5) Control unit- the control unit manage and co-ordinate the entire computer to system. It takes the instruction from the programs stored in the main memory needs the instruction and sends the information to outer units to execute (run) them. (5) A.L.U (arithmetic and logic unit) In an ALU are designing performed the from basic. Arithmetic calculation addition, subtraction, multiplication and division such as less then greater than. (6) Secondary storage unit to store data and final results permanently secondary storage devices are used. Just commonly used of secondary storage devices are hard disks, floppy disk, and C.D etc.

Characteristics of a Computer
(a) (b) (c) (d) (e) (f) (g) Computer is very fast. Computer is accurate. They can process millions of instructions per second. Computer is very versatile. (Unique) Computer works at constant efficiency. (Very high performance) Perform repetitive tasks very well without error. Computer can store information for future retrieval or use. Computer can store information for long time. (h) Computer can communicate with other computer systems.

Generation of computers First Generation -: (1946 - 1954) Use Vacuum Tubes (they were using vacuum tubes) Use Assemble language for programming large in size slow processing speed

Memory capacity ----------10 thousand to 20 thousand character Execution speed ------------few thousand instruction per second.
Example : IBM 704, IBM 709, EDVAC, UNIVAC etc. Second Generation -: (1955-1964) they are Using transistors instead of vacuum tube Increased Operating speeds & improved Storage devices High speed card readers are used in them Memory capacity --------40,000 to 64,000 characters. Execution speed ---------Up to 1 million instruction/sec. Used high-level languages such as FORTRAN and COBOL Line printers and magnetic tape transport units were used in there.

Reduction in size, improved reliability, reduction in operating cost. Example : IBM 1400, IBM 7040, CDC 3600, GE635, B300

Third Generation -: (1965-1974) Use of IC (Integrated Circuit) Memory capacity --------32,000 to 4 million characters. Execution speed ---------up to 10 million instructions per second. Starting use of Semiconductor Memory (RAM or ROM) More miniaturization Reliability and Accuracy Example : IBM 370, Honeywell 200, B2000

Fourth Generation -: (1975-up till now) Use of VLSIC (Very Large Scale Integrated Circuit) and Magnetic Oxide Semiconductor Execution speed ---- 100 million instructions per second. Language --------------all high level language and forth level Languages and artificial intelligence. Operating system speed in nano & pico sec. Refinement of I/O units. Reduction in size. Refinement of HLL and software packages for DBMS Reduced operating cost, recording of errors.

Fifth Generation -: (Development continued...) Will be use ULSIC (Ultra Large Scale Integrated Circuit) Use Artificial Intelligence Super Computer. This type of computer will understand natural languages like English, Hindi etc. and programmer have to instruct only what to do, not how to do. These computers will have full ability to understand sounds and visions & it will reduce the burden of programming.

(1) Analog computers. (2) Digital computers. (3) Hybrid computers.

Analog computersAnalog computers are specific type of computers They are used for some particular types of work only And not for all type of work. It communicate with continuous data and document not communicate with numbers directly i.e.- It uses continues signals as input. These computers are mostly used in engineering and scientific application. Temperature, air pressure, speed, current, weight etc Analog computer calculates the result by measuring the continuous change in these quantities Analog computers do not require any storage capability because they measure and compare quantities in a single operation These Systems are more speedy than digital Examples: Speed meter, air pressure measurement devices, rain gauge etc. Speedometer of a car measure speed in terms of km/h or m/h, the change in temperature is measured by a thermometer in degree s.

Digital computersDigital computers used the binary number systems which has two digits 0, 1. It performs several different tasks. It performs several different generally on counting and not measuring used for business and scientific application. Ex- Pentium III and IV. Digital Computers work on discrete data. Discrete data refers to discrete values such as 0, 1. Digital computers works on 0,1(Binary Numbers) These computers based on the presence or absence of an electrical charge or binary 0 & 1. The native language of this class is therefore called binary language (Machine Language) These Systems are more accurate and precise than others Examples: - calculators, digital watches etc

(3) Hybrid computersIt is a combination of analog computers and also features of digital computers. These computers are mostly used with process control machine like oil refineries and used at places where signals as well as data are to be entered into computer. Combine the best feature of both digital and analog systems Works on both analog and digital data Speedy like analog Accuracy like digital They are used mainly in specialized applications where both analog and digital information needs processing Weather forecasting, Air Defense, Radar Controlling systems, digital petrol pumps etc. In petrol pumps, fuel flow converts into quantity and then quantity is converted into values.


Classification Of Computers With Respect To Size
With respect to size, speed, and cost, we can classify computers in the following types:  MICRO COMPTUERS  MINI COMPUTERS  MAINFRAME COMPUTERS

These computers are small in size. A micro computer use to have Primary memory range from a few Kilobytes to Gigabytes. They are usually designed for personal use therefore they are also called as Personal Computers (i.e. PC). These computers can easily be accommodated (put or keep) on the top of a desk due to their small size and hence are also called as DESKTOP computers. There is another kind of Micro Computer which can easily be placed on the lap and such computer is called as Laptops. These Laptops can be easily carried in a small briefcase. Micro Computers are highly flexible. These are also called CHIP Computers because its entire circuitry is fabricated on a single chip. Examples:-IBM, APPLE, COMPAC, RADIO SHACK, IBM compatibles:- 286,386,486,Pentium-I,Pentium-II,Pantium-III,Pentium-IV etc« Handheld PCs (such as PDAs) lack the power of a desktop or notebook PC, but offer features for users who need limited functions and small size.

These computers are very powerful. Large in size, large in memory and powerful. Mainframe computers are also capable of connecting terminals with it. These computers are used in networked environment and mainly as network servers. Mainframe computers are very expensive.

They are usually designed for the computerization of huge business organizations, universities, banks, scientific laboratories, national and international markets. Multiple Input/output devices are normally attached with a Mainframe computer. The secondary storage use to be in the form disks in a Mainframe computer. Mainframes are measured in integer operations per second or MIPS These computers also allow different users to work on it at the same time like Mini computers but the number of users can be much more than that of the Mini computers (up to thousand¶s users can work at a time on a single Mainframe computer). Examples:- IBM-4381, IBM-360, ICL-2900,NEC-610 etc«

Supercomputer is a computer that is at the frontline of current processing, They have very high capacity, There speed of calculation is very high . Supercomputers are the most powerful computers. They are used for problems requiring complex calculations. It is not possible to consider one computer system as the most powerful, because the power of a computer is not linear and depends on one cpu. Super Computers are very difficult to design, It requires lot of research and development and at the same time they are very much expansive to manufacture. Presently approximately 30-50 Super Computers are sold per annum.

The speed of a super computer is enormous as it was calculated at a rate of 64 billions instructions per second, But now, In terms of computational ability, Supercomputers are more powerful. They have very larger computational power. This will be equivalent to 2 million (1,000,000) laptops. Application in web services and search engines, online banking (Transaction processing), weather forecasting, Climate Prediction, Nuclear weapons (test by simulations), Earthquake and structural modeling and petroleum exploration.

Explain the difference between assembly language and machine language.
Ans. A computer understands information composed of only zeros and ones. A program written in terms of "0s" and "1s" is called a machine language program. Computer instructions are written binary codes. A machine language uses only binary codes. To write a program in a machine language is a very difficult, tiresome and very boring job. Moreover, it is error prone.  To overcome this difficulty a program can be written in alphanumeric symbols instead of "0s" and "1s". Meaningful symbols called mnemonics are used for this purpose. For example ADD is used for addition, SUB for subtraction, CMP for comparison etc. A language, which uses mnemonics, is called an assembly language program. When a program is written in a language other than machine language, the computer will not understand this. Therefore, a program written in other languages must be translated into machine language before it is executed. The task of translation is done by software. A program, which translates an assembly language program into a machine language program, is called an Assembler.

Q. Differentiate a high-level language from an assembly language.
Ans. A language in which each statement or an instruction is directly translated into a single machine code is known as a low-level language. Each mnemonic of an assembly language has a unique machine code. An assembly language is a low-level language. An assembly language depends on the internal architecture of a processor. Each processor has its own assembly language. Assembly language of one processor cannot be used for another processor. In other words it is not portable.

To write an assembly language program, a programmer must have the detailed knowledge of the instruction set of the particular processor, it's internal architecture, registers, and connection of peripherals to ports etc. It is not very fast and easy programming language.

 To overcome the difficulties associated with assembly language, high level or procedure-oriented languages have been developed. In a high-level language an instruction is called statement rather than mnemonic. Statements more closely resemble English and Mathematics than mnemonics. High-level languages permit programmers to describe tasks in the forms, which are problem oriented rather than computer oriented. Programming in a high-level language does not require precise knowledge of the architecture of a processor, which is to be used. A program written in a high-level language will run on any computer, which has a compiler for that language. In other words a high-level language is portable.

Q. Give the difference interpreters.




An Interpreter is a program, which translates statements of a high-level language program into machine codes i.e. in the form of 1 and 0. It translates one statement of the program at a time. It reads one statement of a high-level language program translates it into machine code and executes it. Then it reads the next statement of the program, again translates and executes it. In this way it proceeds further till all the statements of the program are translated and executed.  On the other hand, a compiler goes through the entire high-level language program once or twice and then translates the entire program into machine codes. A compiler is 5 to 25 times faster than an interpreter is. An interpreter is a small program as compared to a compiler. It occupies less memory space, so it can be used in a smaller system, which has limited memory space. The object program produced by the compiler is permanently saved for future reference.

On the other hand, the object code of the statement produced by an interpreter is not saved. If an instruction is used the next time, it must be interpreted once again and translated into machine code. For example, during the repetitive processing of the steps in a loop, each instruction in the loop must be reinterpreted as the loop is executed.

(1)ASSEMBLERSAn assembly language program can not be directly executed by the computer. It has to be converted into its machine language equivalent code before execute it. An assembler is a program that translates a program, written in assembler language into a machine executable code. The input to assembler program is an assembly language program known as source program and output of assembler is a machine language program known as object program. (2)COMPILERCompiler is the translators, which translate high level language program into machine code and this machine code and this machine code is executed after words. The translated machine code is known as object code. Function performed by compiler areo A locate address for all variables and statements. o Generate the object program on tape or disk as required. o Produce listing of source and object program. o Tabulates a list of programming errors found during compilation. Some of the important compiler based languages are PASCOL, FORTRON and TURBO C. INTERPRETERInterpreters are used for translating high level language program into machine level language program line by line and executing each of the instruction alternately. When a program is to be executed, the interpreter accesses the first instruction, translate it into one or more, machine language instructions, and then execute those instructions. The interpreter then accesses the next instruction and repeats these tasks.

The process continuous until all source language instructions have been translated and excited. Features of interpreters(i)Interpreters are slow as compared to compiler because of line by line translation and execution. (ii) Debugging is easier in interpreter based languages because interpretation process stops as soon as error is encountered. (iii) Most well known interpreter based language is basic.

Definition- Usage of operating system-

The usage of operating systems can be define asEasy interaction between users and computer. Computer starts operation automatically, when power is turned on. Loading and scheduling user programs. Controlling input and output. Controlling program execution. Managing use of main memory. Providing security to user s job and files.

An OS is an intermediary between the user of the computer & the computer hardware.

It provides a basis for application program & acts as an intermediary between user of computer & computer hardware. The purpose of an OS is to provide an environment(place) in which the user can execute the program in a convenient & efficient manner. OS is an important part of almost every computer systems. A computer system can be roughly divided into four components o The Hardware o The OS o The application Program o The user The Hardware consists of memory, CPU, ALU, I/O devices, peripherals devices & storage devices. The application program mainly consisted of word processors, spread sheets, compilers & web browsers defines the ways in which the resources are used to solve the problems of the users. The OS controls & co-ordinates the use of hardware among various application program for various users.

Batch Systems:    Early computers where physically large machines. The common I/P devices are card readers & tape drives. The common O/P devices are line printers, tape drives & card punches. The user does not interact directly with computers but we use to prepare a job with the program, data & some control information & submit it to the computer operator.  The job was mainly in the form punched cards.  At later time the O/P appeared and it consisted of result along with dump of memory and register content for debugging.

The OS of these computers was very simple. Its major task was to transfer control from one job to the next. The OS was always resident in the memory.( it is the part of memory) The processing of job was very slow. To improve the processing speed operators batched together the jobs with similar needs and processed it through the computers. This is called Batch Systems. In batch systems the CPU may be idle for some time because the speed of the mechanical devices slower compared to the electronic devices. Later improvement in technology and introduction of disks resulted in faster I/O devices.

The introduction of disks allowed the OS to store all the jobs on the disk. The OS could perform the scheduling to use the resources and perform the task efficiently.

Disadvantages of Batch Systems:1. Turn around time can be large from user. 2. Difficult to debug the program. 3. A job can enter into infinite loop. 4. A job could corrupt the monitor. 5. Due to lack of protection scheme, one job may affect the pending jobs.

Multi programmed System:-

If there are two or more programs in the memory at the same time sharing the processor, this is referred as multi programmed OS. It increases the CPU utilization by organizing the jobs so that the CPU will always have one job to execute. ( more then one program will run on same time) Jobs entering the systems are kept in memory. ( able to store and take jobs as and when required ) OS picks the job from memory & it executes it. Having several jobs in the memory at the same time requires some form of memory management. Multi programmed systems monitors the state of all active program and system resources and ensures that CPU is never idle until there are no jobs. While executing a particular job, if the job has to wait for any task like I/O operation to be complete then the CPU will switch to some other jobs and starts executing it and when the first job finishes waiting the CPU will switch back to that. This will keep the CPU & I/O utilization busy. The following figure shows the memory layout of multi programmed OS

Time sharing Systems:Time sharing system or multi tasking is logical extension of multi programming systems. The CPU executes multiple jobs by switching between them but the switching occurs so frequently that user can interact with each program while it is running. An interactive & hands on system provides direct communication between the user and the system. The user can give the instruction to the OS or program directly through key board or mouse and waits for immediate results. It gives immediate results. A time shared system allows multiple users to use the computer simultaneously. Since each action or commands are short in time shared systems only a small CPU time will be available for each of the user. A time shared systems uses CPU scheduling and multi programming to provide each user a small portion of time shared computers. When a process executes it will be executing for a short time before it finishes or need to perform I/O. I/O is interactive i.e. O/P is to a display for the user and the I/O is from a keyboard, mouse etc. Since it has to maintain several jobs at a time, system should have memory management & protection. Time sharing systems are complex than the multi programmed systems. Since several jobs are kept in memory they need memory management and protection. To obtain less response time jobs are swapped in and out of main memory to disk. So disk will serve as backing store for main memory. This can be achieved by using a technique called virtual memory that allows for the execution of job i.e. not completes in memory. It keeps switching so that memory and the memory management will required. Time sharing system should also provide a file system & file system resides on collection of disks so this need disk management. It supports concurrent execution, job synchronization & communication.

Real- Time Systems:Real time system is one which was originally used to control autonomous systems like satellites, robots, hydroelectric dams etc. Real time system is one that must react to I/p & responds to them quickly. A real time system should not be late in response to one event. A real time should have well defined time constraints. Real time systems are of two types o Hard Real Time Systems o Soft Real Time Systems

A hard real time system guarantees that the critical tasks to be completed on time. This goal requires that all delays in the system be bounded from the retrieval of stored data to time that it takes the OS to finish the request. In soft real time system is a less restrictive one where a critical real time task gets priority over other tasks & retains the property until it completes. Soft real time system is achievable goal that can be mixed with other type of systems. They have limited utility than hard real time systems. Soft real time systems are used in area of multimedia, virtual reality & advanced scientific projects. It cannot be used in robotics or industrial controls due to lack of deadline support. Real time OS uses priority scheduling algorithm to meet the response requirement of a real time application. Soft real time requires two conditions to implement, CPU scheduling must be priority based & dispatch latency should be small. The primary objective of file management in real time systems is usually speeding of access, rather than efficient utilization of secondary storage.

Coaxial Cable
Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a metal shield (See fig. 3). The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.

Fig. 3. Coaxial cable Although coaxial cabling is difficult to install, it is highly resistant to signal interference. No any other signal can disturb the data flow with the help of the coaxial cable. In addition, it can support greater cable lengths between network devices than twisted pair cable. The two types of coaxial o Thin coaxial o Thick coaxial Thin coaxial cable is also referred to as thinnet. 10Base2 refers to the specifications for thin coaxial cable carrying Ethernet signals. The 2 refers to the approximate maximum segment length being 200 meters. In actual fact the maximum segment length is 185 meters. Thin coaxial cable has been popular in Thick coaxial cable is also referred to as thicknet. 10Base5 refers to the specifications for thick coaxial cable carrying Ethernet signals. The 5 refers to the maximum segment length being 500 meters. Thick coaxial cable has an extra protective plastic cover that helps keep moisture away from the center conductor. This makes thick coaxial a great choice when running longer lengths in a linear bus network.

One disadvantage of thick coaxial is that it does not bend easily and is difficult to install.
Coaxial Cable Connectors

The most common type of connector used with coaxial cables is the BNC connector. Different types of adapters are available for BNC connectors, including a Tconnector, barrel connector, and terminator. Connectors on the cable are the weakest points in any network. Data will lose from here more. To help avoid problems with your network, always use the BNC connectors that crimp, rather than screw, onto the cable.

Fiber Optic Cable
Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials (See fig. 5). It transmits light rather than electronic signals. Eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. It is generally used where there is large amount of interference. It has also made it the standard for connecting networks between buildings, due to its immunity (reduces) to the effects of moisture and lighting. Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. These capacity broadband communication possibilities to include services such as video conferencing and interactive services. The cost of fiber optic cabling is comparable to copper cabling; however, it is more difficult to install and modify. 10BaseF refers to the specifications for fiber optic cable carrying Ethernet signals.

Fig.5. Fiber optic cable Fiber Optic Connector The most common connector used with fiber optic cable is an ST connector. It is barrel shaped, similar to a BNC connector. A newer connector, the SC, is becoming more popular. It has a squared face and is easier to connect in a confined space.

Unshielded Twisted Pair (UTP) Cable Twisted pair cabling comes in two varieties: shielded and unshielded. There are two types of twisted pair cable: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks (See fig. 1).

Fig.1. Unshielded twisted pair The quality of UTP may vary from telephone-grade wire to extremely high-speed cable. The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate And the greater the cost per foot.

Categories of Unshielded Twisted Pair Type Use

Category 1

Voice Only (Telephone Wire)

Category 2

Data to 4 Mbps (Local Talk)

Category 3

Data to 10 Mbps (Ethernet)

Category 4

Data to 20 Mbps (16 Mbps Token Ring)

Category 5

Data to 100 Mbps (Fast Ethernet)

Buy the best cable you can afford; most schools purchase Category 3 or Category 5. If you are designing a 10 Mbps Ethernet network and are considering the cost savings of buying Category 3 wire instead of Category 5, remember that the Category 5 cable will provide more "room to grow" as transmission technologies increase. Both Category 3 and Category 5 UTP have a maximum segment length of 100 meters. In Florida, Category 5 cable is required for retrofit grants. 10BaseT refers to the specifications for unshielded twisted pair cable (Category 3, 4, or 5) carrying Ethernet signals. Category 6 is relatively new and is used for gigabit connections. Unshielded Twisted Pair Connector The standard connector for unshielded twisted pair cabling is an RJ-45 connector. This is a plastic connector that looks like a large telephone-style connector (See fig. 2).

A slot allows the RJ-45 to be inserted only one way. RJ stands for Registered Jack, implying that the connector follows a standard borrowed from the telephone industry. This standard designates which wire goes with each pin inside the connector.

Fig. 2. RJ-45 connector Shielded Twisted Pair (STP) Cable A disadvantage of UTP is that it may be affected by radio and electrical frequency interference. Shielded twisted pair (STP) is suitable for environments with electrical interference; however, the extra shielding can make the cables quite bulky. It is used where there is large amount of electrical interference. Shielded twisted pair is often used on networks using Token Ring topology.

Ethernet Cable Summary
Specification Cable Type Maximum length 10BaseT

Unshielded Twisted Pair

100 meters


Thin Coaxial

185 meters


Thick Coaxial

500 meters


Fiber Optic

2000 meters


Unshielded Twisted Pair

100 meters


Unshielded Twisted Pair

220 meters


Coaxial cable A center wire surrounded by insulation and then a grounded shield of braided wire Bundles of glass (or plastic) threads (fibers) to transmit data



-Cable television -Computer networks

Fiber Optics

-Telephone lines -LANs

Twisted-pair cable

UTP (unshielded twisted pair)

Two independently insulated wires twisted around one another Two unshielded wires twisted around each other

-Older telephone networks -Inexpensive LANs -Telephone connections -LANs

-Carries a lot of data -Less susceptible to interference than standard wire -Expensive -Greater bandwidth -Less susceptible to interference than metal wire -Lighter and thinner -Digital data transmission -Very expensive -Fragile -Least expensive

-Easy to work with -Inexpensive -Little bandwidth -Poor protection from interference

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