DATA COMMUNICATION AND NETWORK Terms Communication Communication means to an exchange of information between two or more parties and it can be exchange in a Varity of way. Data or computer Communication is the transmission of data and information over a communications channel between two computers which can be several different things Channel, in communications (sometimes called communications channel), refers to the medium used to convey information from a sender (or transmitter) to a receiver. It is necessary to have a pathway or the media to be transmitted data from one point to another. The term media means the device that transmits the voice or the data form one point to another. Guided Media In Guided media the messages flow through the physical media like twisted pair-wire, coaxial cable fiber optic cables, the media guided is the signal. Coaxial CablingCoaxial cable has a copper core (inner conductor) with an outer cylindrical shell for insulation. it is more expensive and difficult to work with and relatively inflexible and also it cost 10-20 times more then twisted pair.
Twisted Pair Cables
Twisted- pair wire is the most commonly used wire. There are two types of twisted pair cable, shielded and unshielded twisted pair. Shielded twisted pair (STP) cable consists of pairs of insulated solid wire surrounded by a braided or corrugated shielding.
Another type of twisted pair is Unshielded twisted pair (UTP) which is most frequently used network cabling because of It is relatively inexpensive to purchase.
Unshielded twisted pair is telephone wire consisting of wire pairs within an insulated outside covering.
Fiber Optic
Fiber optics consists of thousands of very thin filaments of glass fibers which can conduct lights pulse generated by laser at transmission frequencies that approach the speed of lights. Fiber optics has greater data transmission rate as well as the great security interference tapping.
UnGuided (Radiated) Media:- in unguided media messages is broadcast through the air such as infrared, microwave, or satellite
Infra-Red
There are many systems today using infra-red communications. This is usually a directional infrared light signal transmitted into the air and received by nearby devices.
Radio and Microwave
These are the signals we think of as being radio, television and satellite, but they are now being put to use in wireless Ethernet and Bluetooth communications technologies.
Satellites
The satellite contains a transponder consisting of a radio receiver and transmitter. A ground station on one side of the ocean sends a signal to the satellite, which amplifies it and transmits the amplified signal at a different angle than it arrived at to another ground station on the other side of the ocean.
Signals
Computer uses two types of signals for data transmission are used Analog and Digital.
Digital Signals
A digital signal is a stream of “0” and “1” so this type of signals is appropriate particularly for today computer.
Analog Signals
Analog signals uses variation in a signals to convey information. It is particularly useful for Wave data like sound waves. Our phone lines and speakers are the Examples of Analog Signals.
Modem
Modem word derived from Modulation and Demodulation. A modem is a device that modulates and demodulates the signals. Modulation means conversion of Digital Signals into Analog signals While Demodulation means conversion of Analog signals into Digital signals. Modems are always use in pairs. It is used to connect to the Internet or Global Network.
Network
Te interconnection of more than two computes so that they can share data & resources like printer, CD-ROM is called as a Network.
A Simple Computer Network for File Sharing
Network classification
Networks are classified according to their geographical coverage and size. The two most common network classifications are local area networks (LANs) and wide area networks (WANs).
LANs (Local Area Network)
A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building. On most LANs, cables are used to connect the network interface cards (NIC) in each computer.
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