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Coaxial cable

• Coaxial cable consists of a solid copper wire core surrounded by a plastic cladding shielded in a wire mesh.
• Shield prevents the noise by redirecting it to ground.

Types:

Coaxial cable comes in two sizes which are called thinnet and thicknet.
• Thicknet : is 0.4 inches in diameter and has 50 ohms of electromagnetic impedance
• Thinnet : is 0.2 inches in diameter and has 50 ohms of electromagnetic impedance

USE:

In TV channel communication

Advantages:

• Better than twisted wire cable.
• Popular for TV networks.
• Offers higher bandwidth & Speed

Disadvantages:

• Expensive than twisted wires.
• Not compatible with twisted wire cable.

Optical Fibres

• Thin strands of glass or glass like material designed to carry light from one source to another.
• Source converts (Modulates) the data signal into light using LED (Light Emitting Diodes) or LASER diodes and send it over the Optical fiber.

It consists of three parts:

1. The core: glass or plastic through which the light travels.
2. The cladding : covers the core and reflects light back to the core
3. Protective coating : protects the fiber

Advantages

• Not affected by any kind of noise.
• High transmission capacity
• Speed of Light
• Suitable for broadband communication

Disadvantages

• Installation requires care.
• Connecting two Optical fibers is difficult.
• Optical fibers are more difficult to solder.
• Most expensive

Microwaves

Microwaves are transmitted from the transmitters placed at very high towers to the receivers at a long distance.

Microwaves are transmitted in line of sight fashion, and also propagated through the surfaces.

Advantages

• Maintenance easy than cables.
• Suitable when cable cannot be used.

Disadvantages

• Repeaters are required for long distance communication.
• Less Bandwidth available

Satellite

Geostationary satellites are placed around 36000 KM away from the earth’s surface. In satellite communication transmitting station transmits the signals to the satellite. (It is called up-linking). After receiving the signals (microwaves) it amplifies them and transmit back to earth in whole visibility area.
Receiving stations at different places can receive these signals. (It is called down-linking).

Advantage

• Area coverage is too large

Disadvantage

• High investment

Network devices

Modem

• A modem is a computer peripheral that allows you to connect and communicate with other computers via telephone lines.
• Modem means Modulation/ Demodulation.
• Modulation: A modem changes the digital data from your computer into analog data, a format that can be carried by telephone lines.
• Demodulation: The modem receiving the call then changes the analog signal back into digital data that the computer can digest.
• The shift of digital data into analog data and back again, allows two computers to speak with one another.

RJ- 45 Connector

RJ-45 is short for Registered Jack-45. It is an eight wire connector which is commonly used to connect computers on the local area networks i.e., LAN.

Network Interface Cards (Ethernet Card)

• A network card, network adapter or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network. It provides physical access to a networking medium and often provides a low-level addressing system through the use of MAC addresses. It allows users to connect to each other either by using cables or wirelessly.

Repeaters

A repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances without degradation. In most twisted pair Ethernet configurations, repeaters are required for cable runs longer than 100 meters.

Hubs

A hub is a common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

Bridge

Bridges In telecommunication networks, a bridge is a product that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or token ring). You can envision a bridge as being a device that decides whether a message from you to someone else is going to the local area network in your building or to someone on the local area network in the building across the street.

Switches

A network switch (also called switching hub, bridging hub, officially MAC bridge) is a computer networking device that connects devices together on a computer network, by using packet switching to receive, process and forward data to the destination device. Unlike less advanced network hubs, a network switch forwards data only to one or multiple devices that need to receive it, rather than broadcasting the same data out of each of its ports.

Routers

A router is a networking device that forwards data packets between computer networks. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node.

GATEWAY

A Gateway is a network device that connects dissimilar networks. It established an intelligent connection between a local area network and external networks with completely different structures.




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