Use comparison and contrast to develop a topic by examining its similarities or dissimilarities toanother thing, process, or state. Comparison emphasizes the similarities, contrast the differences. A paragraph may use both comparison and contrast. In the following example, two kinds ofelectrical cable are compared. The aim here is to convey the superiority of A over B for twocategories of performance.
Coaxial vs. Fiber-Optic Cable: Comparative Cable-Length PerformancesFor a number of critical performance characteristics, fiber-optic cable offers considerableadvantages over standard coaxial cables. The most obvious distinction between the two is thegreat bandwidth-distance capacity of fibers. The high-frequency capacity of coaxial cablesdecreases rapidly with increased length, but the bandwidth of a commercial fiber-optic system willremain constant with length. A commercial fiber-optic system like that of Artel, as shown inFigure 3, remains constant for a bandwidth over a distance of 4,000 ft, while three different sizesof coaxial cable rapidly drop in less than half the distance.
For RG-179 coax, a 1,024 × 1,024 signal is limited to 50 ft; RG-59 rolls off 3 dB at 170 ft. Larger, bulkier cables such as RG-11 can reach up to 250 ft, but are impractical to install, sincethree such cables are required for RGB color. Fiber-optic cable, on the other hand, allowstransmission of more than 60 MHz video clock over a mile, and 20 MHz over 2½ miles,with no repeaters or equalizers.
Noise interference is another important area in which performance differs greatly. Coaxial cablesare susceptible to induced interference (EMI/RFI) from such noise generators as fluorescentlights, computers, power cables, industrial equipment, and even other communications cables. Cable frequency equalization further aggravates this noise problem. Fiber-optic cable is, incontrast, immune to all forms of EMI, RFI, and crosstalk.
--Artel Communications Corporation, "Fiber Optics in RGB Color Computer GraphicsCommunications," Application Note CG-1
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