The different technologies used for the data transmission in computers are magnetic media, twisted pair, coaxial cable and optic fiber cable. In the magnetic media method, data is written in a magnetic tape which is transported physically to receiving machine and then data is retrieved. This method is not advisable in geosynchronous communication satellite system and high bandwidth applications. This method is also not economical. The delay characteristics of magnetic tape are poor. Twisted pair is another method of data transmission which consists of two insulated copper wires. Helical shaped wires looks like a DNA molecule and acts like a fine antenna. This is widely used in telephone system where twisted pairs can be operated several kilometers without any amplification. For very long distance operations, repeaters have to be employed. Transmission of both analog and digital signals can be carried out using twisted pairs. The most commonly used twisted pair cabling varieties are category 3 and category 5. Category 3 twisted pairs consist of two insulated wires gently twisted together. Category 5 resembles with category 3 but have more twists. This reduces crosstalk and improves signal quality and transmission speed. Coaxial cables are stiff copper wires surrounded by an insulating material. This allows longer distance transmission at a higher speed. Other advantages of coaxial cables are wide bandwidth and noise immunity. The optic fibers are nowadays used commonly for transmission of data in computers.
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