Re: [hylafax-users] problems with Multitech Modem MT 2834ZDXb

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

On 2003.10.07 12:54 Steve Tuckner wrote:

> People might want to chime in on whether they have had better
> experiences receiving (as that seems to be the major issue) with the
> ConexantFirmware versus AgereFirmware modems in class 1. The
> controller
> code and DSP code for these are obviously different. But in class 1
> the
> only significant difference is the DSP code. I don't have clear data
> on
> which is "better". It probably will depend upon the line conditions
> that
> the particular modem is used on, as different DSP implementations
> handle
> different line impairments better or worse.

Generally speaking I've seen less problems in HylaFAX with 
Rockwell/Conexant-based modems in Class 1 than with Lucent/Agere-based 
modems in Class 1.  For example, I see +FCERROR which later becomes 
fatal on Lucent/Agere-based modems much more than I do on 
Rockwell/Conexant-based modems.  It is a rather small difference, 
however, and of course none of these problems are easily reproducible.

However, I suspect that HylaFAX could do a much better job of handling 
the Lucent/Agere behavior, since HylaFAX Class 1 support seems to have 
been developed with the Rockwell/Conexant chipsets.  For example, 
according to T.31, following the AT+FTM=x from the DTE the DCE must 
respond CONNECT immediately, and then the DCE proceeds in bringing up 
the high-speed carrier.  (Frankly, I think its a stupid specification, 
but that's just how it is.)  The Agere chipsets follow the spec here 
whereas the Conexant chipsets don't.  (The Conexants respond CONNECT 
several hundred milliseconds later, seemingly after the carrier is 
raised.)  Thus we have the Class1TMConnectDelay (currently in HylaFAX 
CVS) config option which is designed to help HylaFAX "cope" with the 
spec-following Agere.  So Agere may not so much be to blame as the fact 
that HylaFAX Class 1 was coded with Rockwell behavior in mind.

Lee.

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