25-08-2017, 09:32 PM
Office Management project on Transmission Medium
TRANSMISSION MEDIUM.ppt (Size: 1.22 MB / Downloads: 35)
TYPES OF TRANSMISSION MEDIUM
GUIDED MEDIUM:
in guided transmission medium signals are guided along the solid transmission medium such as twisted pair, coaxial cable fiber optic.
UNGUIDED MEDIUM:
in unguided transmission medium signals are transmitted through air and outer space such as radio waves. it us also called wireless.
TWISTED PAIR
A twisted pair cable consists of two insulated copper wire about 1 mm thick.
The wires are twisted together in a helical form just like a DNA molecules.
Twisting is done because two parallel wire constitute a fine antenna .when wires are twisted the view from different twist cancel out so the wires radiates less effectively.
The most common application of the twisted pair is the telephone system.
Twisted pair can be used for either analog or digital signals.
COAXIAL CABLE
Another type of transmission medium is coaxial cable.
It consists of a stiff copper wire as a core, surrounded by an insulated material.
The insulated is encased by a cylindrical conductor. the outer conductor is covered in a protective plastic sheet.
Two kinds of coaxial cables are widely used one is 50 ohm and another is 75 ohm.
50 ohm is commonly used for digital transmission.
75 ohm is used for analog transmission.
FIBER OPTIC
Optical fiber is widely used as transmission medium.
It is thin flexible medium through which signals are transmitted in the form of light ray.
Optical fiber is cylindrical in shape which has three parts, core, cladding and jacket.
Core is made of the plastic & glass which is very thin. Core is surrounded by the cladding and cladding is surrounded by jacket.
Data transmission through optical fiber in the form of light.
A pulse of light indicates 1 bit and absence of light indicates 0 bit.
TERRESTRIAL MICROWAVE
Terrestrial microwave has earth based transmitters and receivers.
The frequency used in this transmission is the low ghz range.
Microwave transmission typically used a parabolic antenna that produce a narrow, highly directional signal.
A similar antenna at the receiving sight is sensitive to the signals only within a narrow focus.
Transmitters and receivers are highly focused, they must be adjusted carefully.