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Office Management project on Transmission Medium

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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.

A transmission medium is a material substance (solid, liquid, gas or plasma) that can propagate energy waves. For example, the means of transmitting sounds is usually a gas, but solids and liquids can also act as a means of sound transmission.
The absence of a material medium in a vacuum may also constitute a transmission medium for electromagnetic waves such as light and radio waves. While the material substance is not required for electromagnetic waves to propagate, such waves are usually affected by the transmission media traversing, for example by absorption or by reflection or refraction at the interfaces between the media.

The term "transmission medium" also refers to a technical device which employs the material substance to transmit or guide waves. Thus, an optical fiber or a copper cable is a transmission medium. Not only this but it is also able to guide the transmission of networks.
A transmission medium can be classified as:
• Linear medium, if different waves can be superimposed on any particular point in the medium;
• Limited medium, if it is of finite extension, otherwise half unlimited;
• Homogeneous medium or homogenous medium, if its physical properties do not change at different points;
• Isotropic medium, if its physical properties are the same in different directions.

Electromagnetic radiation may be transmitted through an optical medium, such as optical fiber, or through twisted pair wires, coaxial cable, or slab dielectric waveguides. It can also pass through any physical material that is transparent to the specific wavelength, such as water, air, glass or concrete. Sound is, by definition, the vibration of matter, so it requires a physical medium for transmission, just like other types of mechanical waves and thermal energy. Historically, science incorporated several theories of ether to explain the medium of transmission. However, it is now known that electromagnetic waves do not require a means of physical transmission, and therefore can travel through the "vacuum" of free space. The regions of the insulating vacuum can become conductive for the electric conduction through the presence of free electrons, holes or ions.

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