Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!mips!public!cec
From: cec@public.BTR.COM (Cerafin E. Castillo  cec@btr.com)
Newsgroups: comp.dcom.modems
Subject: Re: Eprom upgreade on TB+. What do I gain?
Summary: T2500 GF7.00 Compatibility with BA5.01...
Keywords: TB+, upgrade
Message-ID: <1508@public.BTR.COM>
Date: 29 Jan 91 19:14:09 GMT
References: <1615@ariadne.csi.forth.GR>
Distribution: comp
Organization: BTR Public Access UNIX, MtnView CA, Contact: cs@btr.com 415-966-1429
Lines: 46

In article <1615@ariadne.csi.forth.GR>, nicolas@csi.forth.gr (Nicolas Chrissakis) writes:
> Hello TB+ modem users,
> 
> I have 3 TrailBlazerPlus modems. The modems have prom version 4.00.
> If I upgrade them to something higher, what will I gain?
> I know that version 5.0 , has bugs. Version 5.01 is OK.
> If I upgrade to 5.01 or higher will I gain anything.
> 

With the introduction of GF7.00 firmware in the T2500/T1500 modems, connection
problems between this firmware level and Telebit modems with BA4.00/BB4.00
firmware have resulted.  Two remedies that I have used for this compatibility
problem have been S120=16 and BA5.01 firmware.

The GF7.00 firmware introduces V.25 tones during a PEP connection in order to
survive noise suppressor/compander weaknesses in long distance carriers such
as MCI and SPRINT.  These weaknesses cause the clipping of PEP packets during
transmission due to the 'kicking-in' of the carriers echo suppressors during
the silent pauses found between PEP packets.  The V.25 tones, found throughout
V.32/V.22bis/Bell212/Bell103 modulations, help keep this from happening by
causing a constant tone during transmission, no more pauses.  BUT, these V.25
tones also cause connection problems with older firmware in TELEBIT modems.

S120=16 disables these V.25 tones and allows easy connections to older
modems.  This might not be suitable for central sites with rotaries on
their modem banks.

BA5.01 is not phased by these V.25 tones.  No changes needed for compatibilty.

I suspect that sooner or later, upgrading will be the only answer to this
problem, not S120=16.  I'm surprised that Telebit has not announced a plan
to better deal with this problem.

Hope this helps and good luck!

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Cerafin E. Castillo                       ||      //\\  ||\\  ||
Network Consultant                        ||     //__\\ || \\ ||  Los Altos
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