A little experimenting

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Hi,

Mizser Krisztian wrote:
> Here's the situation: when faxing from a regular fax machine to another 
> regular fax machine (nearly the same modems, both Panasonic), if during the
> fax transmission I pull the telephone connector out and the plug in again
> (with minimal delay, say 0.5 sec), in the received fax I can clearly see
> those time intervals when the connector was out, the page simply misses
> those lines, but the page as a whole is there.

This means, the fax machine likely just ignores the presence of current on
the line. (Which is reasonable for a fax machine). It's interesting,
though.

> When trying the same fax machine as the sender, and a modem with mgetty 
> on the
> receiving side (E-Tech external 33.6 with AT&T chipset) if I just repeat the
> experiment I described earlier, the modem or mgetty stops reception of the
> page. The fax file ends at the time I pull the connector out, but after
> plugging in again I can clearly hear the incoming fax data, so the telephone
> connection is alive! 

Seems the modem aborts more quickly if it receives too much "garbage"
(un-decodable lines) or if the line current disappears. For whatever
reason.

But I'm fairly sure the standard does not specify a certain behaviour upon
"pulling the plug".

> The reason why I'm doing this is that there is a strange problem I couldn't 
> locate yet that produces nearly the same effects (the reception ends during 
> transmission
> but the incoming fax data can be heared after that, I suspect that there's a
> problem in the telephone network or in a switching equipment, but it needs
> more testing).
> So my question is, how it can be done, that the modem, mgetty behave exactly 
> the same as the fax machine (not to stop the reception, but to skip those lines
> that were sent when the connector was out)

Change the firmware of the modem. The E-Tech Bullet modems are known to
have fairly bad fax firmware, but there is nothing mgetty can do about it
- it's all in the modem.

> PS. Here's a log of such a situation:
> 
> 05/28 13:31:10 yS1 fax_wait_for(CONNECT)
> 05/28 13:31:13 yS1 transmission par.: '+FDCS:0,3,0,2,0,0,0,0'** found **
> 05/28 13:31:15 yS1 fax_get_page_data: receiving /var/spool/fax/incoming/fn38c17
> 75S1.01...
> 05/28 13:31:20 yS1 fax_get_page_data: page end, bytes received: 6398
> 								^^^^^
> 							only 6398 bytes were
> 							received correctly
> 05/28 13:31:21 yS1 fax_wait_for(OK)
> 05/28 13:31:21 yS1 page status: +FPTS:1
> 05/28 13:31:31 yS1 connection hangup: '+FHNG:100'** found **

The modem says "I have a problem, I give up". Nothing mgetty can do.

gert
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