And in addition, if the computer is set to allow data to flow to the modem
at a rate that particular modem can't handle well, things go wrong. If
you have a 28.8 modem and things begin going wrong, you can try setting
your modem speed to 38,400. If you have a 14.4 modem, you can try setting
the modem speed to 19,200. This limits how fast data flows from computer
(DTE) to modem (DCE) so it won't overrun the buffer (lose data and have to
go back and 'get' it again.)
If you dialup to your service provider via modem, you may see a CONNECT
XXXXX message as you make the connection where the XXXXX gives you the
bits per second of the connection. This does not always mean you're
connecting to the service provider at that rate. Some programs show you
the speed from DTE to DCE rather than the connection speed. This adds to
the confusion.
Then, if you have a 28.8 bps modem, you may see a connection of 28800 or
you may see connection rates of 26400 or 24000 (going down in multiples
of 2400 bps.) This relates to the quality of your phone line. To get
the higher speed modems, we send data over every available analog channel
in your phone line. Sometimes one of the channels drops out and the data
transfer rate drops accordingly. Each channel can carry 2400 bps, which
is why the speed drops at those multiples.
Some phone lines are connected to switches from the phone company that do
not handle data speeds greater than 9600 bps. We have some switches like
this locally in Knoxville. One of the temporary fixes to make these
switches give the higher transfer rate is to make some sort of hardwired
connection for each extension. As each of the switches costs upwards of
$10,000 it may be awhile before they are replaced with ones that will
handle data well without the extra wiring.
The above may be why someone mentioned to Bob Evridge that the phone
wouldn't handle more than 19,200. I'd say it's not the phone in that
case, but the setting for the modem speed in the software that had to be
torqued down so it would work properly. I think this also relates to an
init string in the modem (vendor specific) that might help it work
better, as well as making sure that you enable hardware flow-control ONLY
and don't use Xon-Xoff or other flow-control measures.
Niels put together a 'human speak' document about modems which you are
welcome to take a look at. At the bottom is a list of common 'symptoms'
with the probable cause and 'fix' to make it work properly. There is
also a list of common init strings for various modem brands that might be
helpful. http://www.myhome.org/modems.html
Hope this helps.
hht
---: Ms. Holly H. Towne, Director : R E A C H O U T : : - = * OPERATION UPLINK II * = - : a n d : : P.O. B o x 9 7 4 : T O U C H T H E W O R L D : : Knoxville, TN 37901 : towne@usit.net towne@OpUp.ORG :