SSK 20183 - 1.2.3 MEDIA TRANSMISSION

SSK 20183 - 1.2.3 MEDIA TRANSMISSION

by SAASOBAH@NOR ALI

​The Data Communication Component

​1.Sender

2.Message

3.Media Transmission

4.Receiver

5.Protocol

​What is the data transmission mode?

​A data transmission mode describes how two devices in a network communicate or exchange data. It specifics the direction in which signals travel over the media and the number of signals that can traverse the media at any given time.

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​There are THREE types of transmission modes :

1. Simplex

2. Half-Duplex

3. Full-Duplex

​GUIDED TRANSMISSION MEDIA

For any networking to be effective, raw stream of data is to be transported from one device to other over some medium. Various transmission media can be used for transfer of data. These transmission media may be of two types :

​

1. Guided : In guided media, transmitted data travels through cabling system that has a fixed path. For example, copper wires, fibre optic wires, etc.

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2. Unguided : In unguided media, transmitted data travels through free space in form of electromagnetic signal. For example, radio waves, lasers, etc.

​Twisted Pair Cable

​Twisted Pair are copper wires that most common wires used for transmitting signals because of good performance at low costs. To reduce interference between nearby twisted pairs, the twist rates are different for each pair.

​GUIDED TRANSMISSION

​Coaxial Cable

​Coaxial cables are copper cables with better shielding than twisted pair cables, so that transmitted signals may travel longer distances at higher speeds. A coaxial cable consists of these layers, starting from the innermost :

​1. Stiff copper wire as core

2. Insulating material surrounding the core

3. Closely woven braided mesh of conducting material surrounding the insulator

4.Protective plastic sheath encasing the wire

​GUIDED TRANSMISSION

​COAXIAL CABLE

​GUIDED TRANSMISSION

​Optical Fibre

​Thin glass or plastic threads used to transmit data using light waves are called optical fibre. Light Emitting Diodes (LEDs) or Laser Diodes (LDs) emit light waves at the source, which is read by a detector at the other end. Optical fibre cable has a bundle of such threads or fibres bundled together in a protective covering.

Each fibre is made up of these three layers, starting with the innermost layer:

1. Core made of high quality silica glass or plastic

2. Cladding made of high quality silica glass or plastic, with a lower refractive index than the core

3. Protective outer covering called buffer

​GUIDED TRANSMISSION

​OPTICAL FIBER

​GUIDED TRANSMISSION

​Infrared

​Low frequency infrared waves are used for very short distance communication like TV remote, wireless speakers, automatic doors, hand held devices etc. Infrared signals can propagate within a room but cannot penetrate walls. However, due to such short range, it is considered to be one of the most secure transmission modes.

UN​GUIDED TRANSMISSION

​Radio Wave

​Transmission of data using radio frequencies is called radio-wave transmission. We all are familiar with radio channels that broadcast entertainment programs. Radio stations transmit radio waves using transmitters, which are received by the receiver installed in our devices.

Both transmitters and receivers use antennas to radiate or capture radio signals. These radio frequencies can also be used for direct voice communication within the allocated range. This range is usually 10 miles.

UN​GUIDED TRANSMISSION