Re: [hylafax-users] Fax stopped working

[Ross Boylan <RossBoylan@stanfordalumni.org>]

In case it helps, I have a little more info on the fax machines to
which I could not send in Class 2.0 mode.  The recipient writes
"Our fax machines are Panasonics, Panafax 332 and Panafax 585."
Sorry, she didn't say specifically which one mine went to.  She did
note they had been reliable.

From what you say it sounds as if there isn't much of a pattern to the
USR class 2.0 failures.

On Fri, Jul 18, 2003 at 06:52:18AM -0700, Lee Howard wrote:
> On 2003.07.17 23:25 Ross Boylan wrote:
> 
> >It worked!
> 
> Not surprisingly.
> 
> >Though with all the cautions about Class 1, I was a little
> >surprised :)
> 
> Hrmm... but you were.  To what cautions, exactly, are you referring? I 
> guess you mean the "timing considerations" cautions.  I've found them 

Yes, those are the ones--in the hylafax html doc set:

"CLASS 1 MODEM SUPPORT (CAVEAT EMPTOR) HylaFAX includes a driver for modems that support the EIA-578 "Class 1" programming interface. These modems export a very low level interface that requires that the CCITT/ITU Recommendation T.30 facsimile communication protocol be implemented almost entirely in the host. Robust support for this protocol places two requirements on the host system:

    * low latency for serial line input * near realtime response

In a UNIX environment both these requirements can be problematic. In
particular, many UNIX systems increase the latency for data received
on a serial port in order to reduce system overhead. etc..."

> to be unfounded... at least for pentium-class systems with 16 or less 
> modems.  An *extremely* busy system or an extremely old (486?) system 
> may fare differently.
> 
> >It did seem my system became less responsive while the fax was
> >transmitting (I deliberately did very little), but none of my high
> >priority processes looked as if they were associated with the fax.
> 
> Any unresponsiveness was most certainly not fax-related.  If you'd like 
> there to be a chance of it being fax-related you'll need to set 
> PriorityScheduling in the config.

OK, thanks for the info.

> 
> >Is there anyway to have it adaptively fallback to Class 1 if 2.0
> >doesn't work (I gather from some of your charts USR probably doesn't
> >do 2, though I haven't checked)?
> 
> Long story short, Class 2 and Class 2.0 were competing standards 
> proposals, 2.0 being sponsored by USR and 2 being sponsored by 
> Rockwell.  Ultimately 2.0 was adopted even after many manufacturers had 
> already implemented Class 2 equipment.  So no, we'll likely never see a 
> "Class 2" USR.
> 
> As for using Class 1 only in fallback scenarios... no.  I'm sure 
> there's a way to do it, though, but there's no reason to do it that I 
> can think of.

The reason I was thinking of was so stuff would have gone through on
the first try, when it was set to Class 2.0, and to retain the
advantages of Class 2.0 for those recipients with which it worked OK.

But I guess from what you've said that Class 1 works OK, so just using
it all the time is a reasonable solution.

>  Lee.
> 

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