wHATS IS GUIDED MEDIA?
Guided transmission media means the data signals are guided along the path like cabling system.They dont have any other go they have to pass through the given cable or wire.
Guided media are of 4 types :
1. Open wire eg:- Electrical wires from poles.
2. Twisted Pair.
3. Coaxial Cable.
4. Optical Fiber.
1.twisted pair
a cable composed of two small insulated conductors twisted together without a common coveringis konown as twisted pairs . Also known as copper pair.
A thin-diameter wire (22 to 26 gauge) commonly used for telephone and network cabling. The wires are twisted around each other t
o minimize interference from other twisted pairs in the cable (Alexander Graham Bell invented this and was awarded a patent for it in 1881). Twisted pairs have less bandwidth than coaxial cable or optical fiber.
o minimize interference from other twisted pairs in the cable (Alexander Graham Bell invented this and was awarded a patent for it in 1881). Twisted pairs have less bandwidth than coaxial cable or optical fiber.Advantages
It is a thin, flexible cable that is easy to string between walls.
Because UTP is small, it does not quickly fill up wiring ducts.
UTP costs less per meter/foot than any other type of LAN cable.
Disadvantages
Twisted pair’s susceptibility to the electromagnetic interference greatly depends on the pair twisting schemes (usually patented by the manufacturers) staying intact during the installation. As a result, twisted pair cables usually have stringent requirements for maximum pulling tension as well as minimum bend radius. This relative fragility of twisted pair cables makes the installation practices an important part of ensuring the cable’s performance.
In video applications that send information across multiple parallel signal wires, twisted pair cabling can introduce signaling delays known as skew which results in subtle color defects and ghosting due to the image components not aligning correctly when recombined in the display device. The skew occurs because twisted pairs within the same cable often use a different number of twists per meter so as to prevent common-mode crosstalk between pairs with identical numbers of twists. The skew can be compensated by varying the length of pairs in the termination box, so as to introduce delay lines that take up the slack between shorter and longer pairs, though the precise lengths required are difficult to calculate and vary depending on the overall cable length.
Twisted pair’s susceptibility to the electromagnetic interference greatly depends on the pair twisting schemes (usually patented by the manufacturers) staying intact during the installation. As a result, twisted pair cables usually have stringent requirements for maximum pulling tension as well as minimum bend radius. This relative fragility of twisted pair cables makes the installation practices an important part of ensuring the cable’s performance.
In video applications that send information across multiple parallel signal wires, twisted pair cabling can introduce signaling delays known as skew which results in subtle color defects and ghosting due to the image components not aligning correctly when recombined in the display device. The skew occurs because twisted pairs within the same cable often use a different number of twists per meter so as to prevent common-mode crosstalk between pairs with identical numbers of twists. The skew can be compensated by varying the length of pairs in the termination box, so as to introduce delay lines that take up the slack between shorter and longer pairs, though the precise lengths required are difficult to calculate and vary depending on the overall cable length.
CO-AXIAL CABLE
A cable consisting of a conducting outer metal tube that encloses and is insulated from a central conducting core, used primarily for the transmission of high-frequency signals. Also called coaxial line.
1.A cable consisting of two concentric conductors (an inner conductor and an outer conductor) insulated from each other by a dielectric; commonly used for the transmission of high-speed electronic data and/or video signals. 2. A single transmission cable having a concentric conductor and shielding; used for communications transmission, such as for television signals.
advantages
advantages
Coaxial cables were designed to solve a problem with the transmission of high frequency radio signals. Information load increases with frequency, so RF was the practical vehicle for high volume long distance communications. These transmissions are line-of-sight signals that attenuate rapidly and escape into space--coaxial cable confines the signal to the cable interior and makes efficient transmission to any location possible.
limitations
limitations
Along the length of the coaxial cable, part of the transmitted signal will be lost or attenuated. A small percent may escape the cable's shielding and more will be converted to heat. The higher the frequency, the greater the losses. For very long distance transmissions repeater stations are necessary for amplifying and retransmitting weakened signals. The upper frequency limit of the coaxial design is about 4 GHz, and the practical bandwidth of high efficiency coaxial is able to meet most current data needs
optical fibres
