Using many modems

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Hi,

On Thu, Nov 05, 1998 at 07:20:10PM +0100, Oliver Sturm wrote:
> > only to *one* modem at a time.  If that one is busy, use the next one.
> > 
> > Having all modems RING at the same time is a bad idea for obvious reasons
> > (locking, lots of failed calls, modem reinitialization dead time, etc.).
> > 
> > Effectively, make your telephone system view the modems as a "hunt group"
> > 
> Well, I didn't really have the idea of configuring my telephone system
> to do that work for me... seems pretty easy that way. Anyway, the
> problem is still the same to me, because I know lots of people who have
> a telephone system that doesn't have such a function (my small company
> included). 

Huh?  Usually, PBXes ("telephone systems") that have many ISDN lines also
can do hunting etc. - only the SOHO systems have to do "ring all lines at
once".

> What's more, people might be attaching up to seven (or was it
> eight) modems (or terminal adaptors) to an ISDN-line without any
> telephone system, so all these devices continue to get the RING at once. 

What would that be good for?  You can hook up 8 devices to an ISDN line,
but only two of them can be active at a given time.  So that's a pretty
useless scenario.

For two devices, the ISDN bus does the device locking, so only *one* of
the devices will get the call, the other won't (on the ISDN layer).

> Gert, no offense ment, but the behaviour of mgetty, if it gets several
> rings at once coming from the same call, isn't plausible. 

Three things:

a) one mgetty process doesn't know *anything* about other mgetty
processes

b) mgetty processes MUST NOT care about other stuff running on the same
system.  For me, it's not very unusual to have two modems RING at the
same time - I have customer systems that have eight analogue phone lines,
and they DO get calls on different modems at the same time.

c) I have always refused to break mgetty to handle broken scenarios.  A
scenario where two (or more) modems get a RING for one call is already
broken, but a scenario where those modems interfere with each other when
answering is SO horribly broken that I flatly refuse to even think about
it.

(If they don't interfere with each other, it won't really do much harm to
answer on both modems - one will get the call from the PBX, and one
won't, so no harm will happen).

> I'll have to
> see if I still got those old logs where you can see that two running
> mgetty-instances kind of "take away" the call from each other.

Just the fact that one modems returns "FAX" when talking to a dead line
doesn't mean too much.  My old discovery 2400P is able to get a 300bps
CONNECT with the dial tone... :)

gert
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Gert Doering - Munich, Germany                             gert@greenie.muc.de
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