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Re: [hylafax-users] HDLC frame not byte-oriented

Andrew Rinaldi wrote:
If you changed from a USR to a Venus (this is important) based MultiTech and
had no improvement then you need to look elsewhere for your issue.  Once
this issue is resolved you will be glad that you have the Venus chipset.

In my opinion the missing Class 1 features of +FCERROR support and proper +FRS/+FTS support make the USR a no-go on any high-volume production server. Those features, properly implemented as on the Lucent/Agere Venus and the Agere/LSI CFAX34 ... as well as on many Rockwell/Conexant [hardware] chipsets... make them far more valuable for reliable Class 1 faxing.

The V.34-Fax support on the Venus and CFAX34 make it particularly attractive.

On the later Rockwell and all Conexant chipsets (again, I'm not talking about winmodem/linmodems here) there is also support for +FAR=1 which makes unexpected signal handling particularly easy, and is a nicety not on the Agere/LSI chipsets... however, its behavior can be closely approximated through use of the supported +FCERROR indication/result where +FAR=1 is not supported. The nicer thing about +FAR=1 is that it indicates that the chipset manufacturer was conscientious about V.21 HDLC detection... and it gives credibility to a "CONNECT" after AT+FRH=3 (which should *only* ever mean that V.21 HDLC was detected... not just any noise). Thus we don't see the need for Class1HasRHConnectBug on those Rockwell/Conexant modems as we do with Agere/LSI.

In any case, the USR modems have been among the poorest-performing that I've worked with. The biggest problem, I believe, is that USR/3Com has, to my knowledge, not worked openly with fax application developers and their users to make things better. Their fax development is a slow, slow process. Most of what you see in their fax modem features (and many of the bugs) existed ten years ago in the TI chipset that became the basis for their fax modems.



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