Instructor: In the last lesson,
we just finished talking about DSL,
and I mentioned that there's a decline in popularity
because cable modems and fiber modems started taking over.
So let's talk about cable modems for a moment.
Cable modems use the cable TV network,
which is made up of a hybrid fiber-coaxial solution,
notice HFC, and this is the type of
distribution network it has.
If you see the term HFC on the exam,
remember we're talking about cable modems here.
Now cable TV can ride on top of it,
but so can our internet signals.
And so this mixture of coaxial and fiber cables
made it very fast.
There's specific frequency ranges that are used
for upstream and downstream transmissions
as determined by a standard called DOCSIS,
which is Data-Over-Cable Service Interface Specification,
D-O-C-S-I-S, so again, for the exam,
anytime you see HFC or DOCSIS,
I want you to think about the answer
being something to do with cable modems.
Now upstream, these use between 5 and 42 Mhz,
and downstream, they use between 50 and 860 MHz.
Don't worry about those frequencies for the exam,
just remember the terms HFC and DOCSIS are associated
with cable modems, and you'll do fine.
Now, these systems can transmit and receive
over the current cable TV infrastructure,
which has already rolled out to most of America
and many other places worldwide.
And this made it a very quick sale
to get cable modems into the marketplace,
and they offered increased speed over DSL,
which made them even more popular.