WEBVTT



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<v Instructor>In the last lesson,</v>



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we just finished talking about DSL,



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and I mentioned that there's a decline in popularity



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because cable modems and fiber modems started taking over.



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So let's talk about cable modems for a moment.



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Cable modems use the cable TV network,



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which is made up of a hybrid fiber-coaxial solution,



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notice HFC, and this is the type of



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distribution network it has.



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If you see the term HFC on the exam,



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remember we're talking about cable modems here.



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Now cable TV can ride on top of it,



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but so can our internet signals.



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And so this mixture of coaxial and fiber cables



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made it very fast.



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There's specific frequency ranges that are used



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for upstream and downstream transmissions



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as determined by a standard called DOCSIS,



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which is Data-Over-Cable Service Interface Specification,



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D-O-C-S-I-S, so again, for the exam,



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anytime you see HFC or DOCSIS,



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I want you to think about the answer



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being something to do with cable modems.



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Now upstream, these use between 5 and 42 Mhz,



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and downstream, they use between 50 and 860 MHz.



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Don't worry about those frequencies for the exam,



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just remember the terms HFC and DOCSIS are associated



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with cable modems, and you'll do fine.



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Now, these systems can transmit and receive



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over the current cable TV infrastructure,



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which has already rolled out to most of America



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and many other places worldwide.



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And this made it a very quick sale



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to get cable modems into the marketplace,



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and they offered increased speed over DSL,



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which made them even more popular.