mgetty / Zyxel problem

• Messages sorted by:[ date ][ thread ][ subject ][ author ]

Hi,

(CC:ed to the mgetty list, 'cause I'm a bit short of time, and don't
really have an idea what might be causing this).

Usually, missing stripes on the fax are caused by overruns on the sender
side, because of lack of proper flow control.  But you have provided
enough evidence that it's NOT the sender side.

Farzin Atefi has reported a similar problem earlier this year (missing
lines upon fax reception), and I couldn't help him either.  If I remember
correctly, he had a ZyXEL 1496 as well, but I don't know the firmware
version.

I run my favourite fax modem with 6.12P, and haven't ever seen this problem.

I haven't tested newer versions as thoroughly, so I can't say whether it's
a firmware or maybe modem hardware bug, or whatever.  OTOH, there is a 
version 6.19 by now, so there must have been some lurking bugs in 6.15...

Maybe you can compare notes with other 1496-users on the mgetty list
(mgetty@muc.de), and you can find out which firmware versions are "bad" .
I will then write this down into the mgetty docs.

Firmware upgrades are fairly easy, but you need someone who can burn you
an updated set of EPROMs.  I could, but I won't be in .NL again before 
January (RIPE meeting in Amsterdam), so shipment will be expensive & slow...

gert



On Wed, Sep 16, 1998 at 11:27:17AM +0200, Rob van Nieuwkerk wrote:
> I have a problem that's driving me nuts: It seems that I can *not*
> reliably receive faxes at 14400 bps signaling rate.  The problem
> shows clearly when sending complex graphics.
> 
> There is some overrun happening somewhere.  I use the ghostscript
> tiger.ps for my experiments.  The symptoms are that every 4-6 cm
> there is a piece of the fax missing (not a single line but several
> consecutive lines).  It appears that if the data is easier to compress
> (eg. round the mouth where there's lots of white) it takes longer
> for the next overrun to appear. So I think it's definately an overrun
> problem.  But where ??
> 
> This is my setup:
> 
> Linux 2.0.35
> mgetty+sendfax 1.17
> ZyXEL U-1496E (ROM v 6.15)
> Ghostscript 5.10 (not relevant I think)
> 
> I have 2 machines (and 2 ZyXELs) for testing.  The serial ports are well
> configured 16550A's with OK cables.  And I think that I configured the
> mgetty/sendfax ports OK (mailed with you about this earlier):
> both FAXSEND_FLOW and FAXREC_FLOW are (FLOW_HARD | FLOW_SOFT).
> 
> Many experiments with different settings & faxmachines lead me to these
> conclusions:
> 
> - the problem is on the *receiving* side.
> - if the data (on the phone-line) is coming in faster than 9600 bps
>   there is a problem:
> 
> send port	receive port	signalling speed	problem
> -----------------------------------------------------------------
> 38400		38400		14400			yes
> 9600		38400		14400			no
> 38400		38400		9600			no
> 
> - sending to *other* faxes is OK for all speed combinations.
> - same tests with HylaFax give the same results
> - the problem appears at the same postion for different experiments.
>   This could indicate a problem related to the data content.  But
>   at 9600 bps things are OK !
> 
> I've read all the mgetty documentation.  There nothing but praise
> about the ZyXELs (the manual literaly states that with the right ROM
> version tiger.ps should work like a charm !)  But I'm starting to suspect
> there is a *modem* problem.
> 
> So my questions are:
> 
> - Am I looking over something obvious  or a "secret" setting ?
> - Do you know about any problem with my ZyXELs that fits the symptoms above ?
> - A "solution" for me would be if I could force my *receiving* modem to not
>   go higher than 9600 signalling speed.  Am I right that such setup would
>   require changes in the mgetty *source* ? (I know about the "fax-max-speed"
>   for *sendfax*.  Would be nice if it was available for mgetty too.)
> 
> Please mail me if you want other/more information !
> 
> 	Greetings,
> 	Rob van Nieuwkerk

-- 
USENET is *not* the non-clickable part of WWW!
                                                           //www.muc.de/~gert/
Gert Doering - Munich, Germany                             gert@greenie.muc.de
fax: +49-89-35655025                        gert.doering@physik.tu-muenchen.de