File Name: data communications and computer networks .zip
Converting Data into Signals a.
- Data Communication and Networking Notes, PDF | B Tech 2021
- Data Communications and Computer Networks
- Data Communications and Networking By Behrouz A.Forouzan
- data communication pdf
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Data Communication and Networking Notes, PDF | B Tech 2021
The message of course is central to all the components. The message is the data that is being communicated. Fig 2. It can be a computer, workstation, telephone handset, video camera, and so on. Twisted-pair cabling consist of copper wires that are twisted into pairs. Ordinary telephone wires consist of two insulated copper wires twisted into pairs. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction.
The transmission speed ranges from 2 million bits per second to 10 billion bits per second. The cables consist of copper or aluminum wire wrapped with insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer. The layers of insulation help minimize interference and distortion. Transmission speed range from million to more than million bits per second. It transmits light which can travel over extended distances.
Fiber-optic cables are not affected by electromagnetic radiation. Transmission speed may reach trillions of bits per second. The transmission speed of fiber optics is hundreds of times faster than for coaxial cables and thousands of times faster than a twisted-pair wire. This capacity may be further increased by the use of colored light, i. Instead of carrying one message in a stream of monochromatic light impulses, this technology can carry multiple signals in a single fiber.
The equipment looks similar to satellite dishes. Terrestrial microwaves use low-gigahertz range, which limits all communications to line-of-sight. Path between relay stations spaced approx, 48 km 30 mi apart.
Microwave antennas are usually placed on top of buildings, towers, hills, and mountain peaks. The satellites are stationed in space, typically 35, km 22, mi for geosynchronous satellites above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals. Bandwidth is the range of frequencies that is available for the transmission of data.
A narrow range of frequencies in a communication system is analogous to a garden hose with a small diameter. The flow of information in such a system is restricted, just as is the flow of water in the narrow hose. Wider bandwidths permit more rapid information flow.
The communication data transfer rate is measured in a unit called baud. Baud is identical to bits per second. Therefore, a rate of baud is bits per second. Data transmission rates are from 45 to baud. The low-speed devices might use narrow band communications. They are used for applications ranging from operating a CRT to running a line printer. Their major application is for telephone voice communication hence, the term voiceband.
MODEMA modem modulator-demodulator is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from light emitting diodes to radio. A modem modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted pair telephone line and demodulates the incoming analog signal and converts it to a digital signal for the digital device.
In recent years, the bits per second modem that could carry e-mail has become obsolete. From early , most new personal computers came with 56 Kbps modems. By comparison, using a digital Integrated Services Digital Network adapter instead of a conventional modem, the same telephone wire can now carry up to Kbps. With Digital Subscriber Line DSL systems, now being deployed in a number of communities, bandwidth on twisted-pair can be in the megabit range.
A telephone cable with a RJ plug connects the modem to the nearest phone jack, which also conforms to the RHstandard. Landline modems can be further classified into the followings types: Internal modems:This device is a circuit board that plugs into one of the expansion slots of the computer. Internal modems usually are cheaper than external modems, but when problems occur, fixing and troubleshooting the modem can sometimes prove to be quite difficult.
The telephone line plugs into the modem port in the back of the computer. Most internal modems come installed in the computer you buy. Internal modems are more directly integrated into the computer system and, therefore, do not need any special attention. Internal modems are activated when you run a communications program and are turned off when you exit the program.
This convenience is especially useful for novice users. Internal modems usually cost less than external modems, but the price difference is usually small. The major disadvantage with internal modems is their location: inside the computer. When you want to replace an internal modem you have to go inside the computer case to make the switch. External modems:This device is attached to the back of the computer by way of a cable that plugs into the modem port.
It is usually less expensive and very portable. It can be used with other computers very easily by unplugging it and plugging it into another computer. This is the simplest type of modem to install because you don't have to open the computer.
External modems have their own power supply and connect with a cable to a computer's serial port. The telephone line plugs into a socket on the rear panel of the modem. Because external modems have their own power supply, you can turn off the modem to break an online connection quickly without powering down the computer.
Another advantage over an internal modem is that an external modem's separate power supply does not drain any power from the computer. You also can monitor your modem's connection activity by watching the status lights. Your computer can also send information to a fax machine. Most computer modems are modems with faxing capabilities. PC Card modem:These modems, designed for portable computers, are the size of a credit card and fit into the PC Card slot on notebook and handheld computers.
These modems are removed when the modem is not needed. Except for their size, PC Card modems are like a combination of external and internal modems. These devices are plugged directly into an external slot in the portable computer, so no cable is required other than the telephone line connection.
The cards are powered by the computer, which is fine unless the computer is battery-operated. Running a PC Card modem while the portable computer is operating on battery power drastically decreases the life of your batteries. Using wireless modems, one can connect to a network while being mobile. Unlike landline modems, wireless modems do not plug into an RJ jack. Working of ModemModems convert analog data transmitted over phone lines into digital data so that computers can read; they also convert digital data into analog data so it can be transmitted.
This process involves modulating and demodulating the computer's digital signals into analog signals that travel over the telephone lines. In other words, the modem translates computer data into the language used by telephones and then reverses the process to translate the responding data back into computer language. In computer network two or more computers are linked together with a medium and data communication devices for the purpose of communicating data and sharing resources.
The computer that provides resources to other computers on a network is known as server. In the network the individual computers, which access shared network resources, are known as nodes. Networks may be classified according to a wide variety of characteristics such as the medium used to transport the data, communications protocol used, scale, topology, and organizational scope. The rules and data formats for exchanging information in a computer network are defined by communications protocols.
Properties of Network Facilitate communications:Using a network, people can communicate efficiently and easily via email, instant messaging, chat rooms, telephone, video telephone calls, and video conferencing.
Permit sharing of files, data, and other types of informationIn a network environment, authorized users may access data and information stored on other computers on the network. The capability of providing access to data and information on shared storage devices is an important feature of many networks. Share network and computing resourcesIn a networked environment, each computer on a network may access and use resources provided by devices on the network, such as printing a document on a shared network printer.
Distributed computing uses computing resources across a network to accomplish tasks. Not only can you share photos, music files, and documents, you can also use a home network to save copies of all of your important data on a different computer. Backups are one of the most critical yet overlooked tasks in home networking. No longer will you need to bounce from one system or another just to print out an email message.
Data Communications and Computer Networks
Master of Computer Application Year 2 candidates those who are searching for the Data Communication and Networks Book we have been provided the complete details like important topics, and the download links of the subject , etc mentioned in this article. So, read the complete article and the candidates can know more details of the subject. Data Communication and Networks means the transmission of digital data between more than two computers and a data network is a telecommunications network that allows computers to exchange data. Important Topics of this subject was mentioned below for the candidates to refer to. There are 4 important topics of the subject.
Computers may connect to each other by either wired or wireless media. Classification of Computer Networks. Computer networks are classified based on various.
Data Communications and Networking By Behrouz A.Forouzan
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data communication pdf
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Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. Halsall Published Computer Science. Part One: Data Communications 1. Data communication networks and open system standards 2. The electrical interface 3. Data transmission 4.
Сьюзан была озадачена. - Это по-латыни, - объяснил Хейл. - Из сатир Ювенала. Это значит - Кто будет охранять охранников?. - Не понимаю. Кто будет охранять охранников. - Вот .
PDF | On Sep 10, , Dr H Shaheen and others published Data Communications and Computer Networks | Find, read and cite all the.
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