Modems
...28.8 or 33.6 kbps (V.34) modems, under ideal phone line conditions, will
transmit and receive data at 28,800 or 33,600 bits per
second, and 56K (X2, K56, or V.90 modems) will typically transmit data at up
to 33.6 kbps, and receive data at up to about 50,000 kbps (more or less).
Because all of these modems can use data compression, they can achieve
throughputs ...
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...You probably know that modems are analog devices. You may not know, however,
the telephone system in the US is a mix of analog and digital. Almost all calls
in US are converted from analog to digital at your local phone company office,
and stay digital until they reach the local loop of the place you call. So what
is going on is we start with digital data at our computer, convert it to analog
in our modem, and send it out to the phone system. The phone company switches it
back to digital and transmits it, then converts it back to analog for the local
loop at the other end. There, the modem converts it from analog back to digital
for the remote computer... >>>
...The latest modem standard is V.92, which was determined by the ITU
(International Telecommunications Union) at the end of 2000. Modems using
this standard are still 56K modems, but three new features have been added
-- faster connections, better uploading, and, data and voice support...
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..."Software Modems" (or "Soft Modems" as they are sometimes called) are
modems which transfer many or most of the modem functions to software
which uses your PC's CPU rather than performing them within the modem
itself. This allows the manufacturer to produce a modem with very few
parts on it (a HSP modem is little more than a host interface card and an
associated modem software program), which greatly reduces their cost. It
also allows some modem upgrades via software downloads rather than
requiring firmware upgrades. In the early days of this type of modem, many
users experienced substantial problems... >>>
...Over the last couple of years there has been
lots of talk about cable modems -- modems that would hook to your TV cable, and
let you get very high speed internet access. Availability is still limited in
many areas, but is growing rapidly. Serious bandwidth problems would be
experienced by most cable companies if they brought cable modems into wide use
too rapidly which is one of the reasons implementation has not been fast. Some
of the big cable companies are starting to use digital technologies that would
partially address that problem. Some users of cable modems have complained that
their access speeds have dropped by a factor of 4 or more as more customers sign
up for the service... >>>
...DSL stands for Digital Subscriber Line, a
service being provided by some telephone companies, with support by some ISPs.
It provides normal voice service plus simultaneous Internet access at speeds up
to 1.5 Mbps (or considerably higher in some cases) using a relatively new
technology that runs over standard phone lines. While a couple of years ago it
appeared that ISDN would be the next generation of technology that individuals
would use for higher-speed access over phone lines, now it is clear that DSL is
the favored technology for consumer service due to the fairly low implementation
cost... >>>
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