Differences between current version and revision by previous author of MoDem.
Other diffs: Previous Major Revision, Previous Revision, or view the Annotated Edit History
| Newer page: | version 5 | Last edited on Friday, May 5, 2006 11:30:30 pm | by LawrenceDoliveiro | |
| Older page: | version 4 | Last edited on Wednesday, September 7, 2005 7:48:58 am | by AristotlePagaltzis | Revert |
@@ -1,7 +1,10 @@
-An abbreviation of __Mo__dulator/__Dem__odulator, a device used to transmit data via phone
line.
+An abbreviation of __Mo__dulator/__Dem__odulator, a device used to transmit/receive digital
data via an analog communication channel. Common kinds of modems:
+* acoustic modem -- the original kind of modem, where the analog channel is a telephone voice
line. These days most commonly used for dial-up Internet access, once upon a time also heavily used for connecting to [BBS]es.
+* ADSL modem -- connects to [ADSL] service, which takes advantage of the fact that the copper wires used for telephone landline service have a much greater bandwidth than is needed for just voice.
+* cable modem -- connects to an Internet service provided by a cable TV company
.
-The name stems from the fact that it modulates an audio signal according
to the stream
of bits sent to it
by a computer so
that it
can be sent across a phone line. Meanwhile, it detects modulation of
the incoming signal to reconstruct the original stream of bits it was made from
, which is then sent
to the computer. Thus, you can network two computers with MoDem~s via a phone connection
.
+''Modulation'' refers
to any kind
of technique whereby a ''carrier'' signal output
by the transmitting end has its characteristics altered in some systematic way
that can be detected by
the receiving end
, in order
to convey information
.
-''AddToMe: does this
still apply
to CableModem~
s?''
+Most kinds of modems nowadays are not symmetrical--they are designed to communicate with special equipment belonging to a central service provider, not with a modem bought by another ordinary person-off-the-street. Acoustic modems
still have symmetrical communication capability, but only at speeds up
to 33.6kb/s (V.34). The higher 56kb/
s speed (V.90) only works with special equipment at the provider end.
-Most modern MoDem~s, so-called WinModem~s, do not contain the hardware necessary to perform all of this operation. Instead, they rely on the host [CPU] for much of the signal processing. Because the software to do this is part of the MoDem driver, and many vendors write drivers only for MicrosoftWindows, some WinModem~s cannot be operated under [Linux].
+Most modern acoustic
MoDem~s, so-called WinModem~s, do not contain the hardware necessary to perform all of this operation. Instead, they rely on the host [CPU] for much of the signal processing. Because the software to do this is part of the MoDem driver, and many vendors write drivers only for MicrosoftWindows, some WinModem~s cannot be operated under [Linux].
