August 1998--You have
installed your shiny new 56K modem, and you are now enjoying
increased download speeds. Your next step is to connect it to a
friend's 56K modem.
OK, where did the speed increase go?
56K depends on the special
relationship that the Internet service provider (ISP) has with your
local telephone company, and how the telephone company and your
modem operate. Modems are analog devices. They send and receive
information as a series of sound waves. If you were really wiggy and
cool, you could get on your telephone handset and make noises like a
modem does and "talk" to another modem. Note that I'm not aware of a
human that has actually done this, although I have some friends
about whom I'm not so sure.
Computers, on the other hand, are
digital devices. They deal with zeros and ones, not sound waves. The
modem's job is to convert the signals from digital (the computer
end) to analog (the telephone end). The term "modem" is derived from
the terms "Modulation/De-Modulation," which means converting from
analog to digital and back again.
Modern telephone switching equipment
is now able to handle digital signals directly and this makes 56K
possible. The finer details of this technology are complex but the
engineers tell us that the best we can get from the copper wire and
the older switching equipment is 33.6K. To go faster, some of the
conversions from analog to digital and back must be removed. That's
exactly what happens with 56K. The ISP and the telephone company get
together and build a digital link between their two offices. This
means the only conversion from digital to analog occurs when the
signal is sent to your phone line.
If you have been having problems
getting a 56K connection to work, you will want to test your line to
make sure there is only one analog-to-digital conversion happening.
The folks at 3COM have a test that you can run to check your line.
Visit 3COM's site at
http://www.3com.com/56k/need4_56k/linetest.html for complete
details.
When you connect with your friend,
you have more than one analog/digital conversion in the connection
and one at your friend's end. This is why 56K doesn't work between
two 56K modems.
Next month, we'll examine some other
methods of sending information from one system to another.
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