[TriLUG] A Slow Serial Modem

[Maxwell Spangler]

yOn Sat, 21 Jan 2006, Brian Bell wrote:

> To do this project, we purchased a Creative Labs-Modem Blaster 56K V.92 
> External Modem-DE5621 from Best Buy. For whatever reason, we can't seem to 
> get it to connect to the old system at a slow enough speed. 
> So ... my question is twofold.
>   1. does anyone have any experience in this area? ie. connecting modern day 
> stuff with 20+ year old equipment? and/or any experience with this modem?

Yes.  I worked in an industry where the primary means of communicating all 
critical data on a daily basis was done via analog modems from call centers to 
hundreds of receiving stations.  Although modems are supposed to follow 
standards you will encounter situations where two just won't work with each 
other.  This is especially true when you pair an old 1200 baud modem with no 
error correction or data compression with a new 56k modem that does many more 
speeds and many more 'advanced' features.

I would recommend you try either of two solutions to the problem.  First, you 
can get a manual for the creative and find the programming commands ("AT" 
commands and "S" register settings) in order to reprogram the modem. 
Reprogram the 56k to act like a 1200 by turning off data compression, error 
correction and only being able to connect at 1200 bps.  This often resolves 
problems that are encountered when the more modern 56k modem tries to 
negotiate advanced features with an older modem. The older modem knows nothing 
off these and often cancels the negotiation or times-out prematurely.  SO make 
the 56k dumb and things often work.

The second solution is simply to replace the creative brand 56k with another 
brand, like a usr.   Creative and/or the chipset used in the creative may just 
not be compatible with the old 1200 you've got installed, but another brand 
might.

On my systems I would have one system receiving from many call centers -- 
usually 4-5.  But because each call center used different analog modems to 
transmit I often had to reprogram the receiving equipment to disable features 
as described above and I had better results.  But it was not uncommon to find 
me buying old hayes 2400 baud modems because that was the only thing that 
would work on my system to receive from a call center using hayes 2400 baud 
modems to send.

hth.

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Maxwell Spangler
Chapel Hill, North Carolina