Path: utzoo!utgpu!watserv1!maytag!xenitec!zswamp!root
From: root@zswamp.uucp (Geoffrey Welsh)
Newsgroups: comp.dcom.modems
Subject: V.42bis vs. MNP5
Message-ID: <30.28280172@zswamp.uucp>
Date: Wed, 08 May 91 03:26:33 EST
Organization: Izot's Swamp BBS (FidoNet), Kitchener, Ontario

In a letter to All, Dave Rubin (drubin@prism.poly.edu ) wrote:

 >I am in the process of upgrading our dialup modems, most 
 >likely with some combination of 9600bps and 2400bps modems.
 >Our telephone switch cannot handle async speeds over 19.2kbps.

   I'm not sure that this has any effect on the choice of modems, unless the 
modems will be used to transmit data generated by the telephone switch itself, 
which is unusual or possible.

   If the telephone switch is just a PBX and the modem's serial port is being 
plugged into another computer, then this isn't an issue at all.

   If the switch is digital and has a low sampling rate, you may have a 
problem with higher speed modems; only experimentation (or the voice of 
experience) will be able to tell what the maximum reliable speed will be.

   In any case, the maximum physical bit rate of V.32 modems is 9600, and of 
V.32bis modems it's 14400.  V.42bis doesn't increase the speed at which the 
two modems communicate with each other, and its presence or absence should 
have no effect on whether a line will support a certain speed.

 >Therefore, the potential 38.4kbps throughput of V.32/V.42bis
 >modems would probably be wasted.

   Keep in mind that this "potential" is the result of data compression, which 
does not in any way affect the rate the real data bits are passed through the 
phone line!
 

--  
Geoffrey Welsh - Operator, Izot's Swamp BBS (FidoNet 1:221/171)
root@zswamp.uucp or ..uunet!watmath!xenitec!zswamp!root
602-66 Mooregate Crescent, Kitchener, ON, N2M 5E6 Canada (519)741-9553
"He who claims to know everything can't possibly know much" -me