Using many modems

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Marc Eberhard <marc@athene.thphy.uni-duesseldorf.de> writes:
> The switch sends a SETUP message. All connected devices send back a
> SETUP ACKNOWLEDGE message (if they decided based on the information
> in the SETUP message, that they should answer that call at all). Now
> these devices start to alert the user and send back an ALERTING
> message. As soon as the first user picks up, that device sends a
> CONNECT message to the switch. The switch acknowledges this with a
> CONNECT ACKNOWLEDGE message. It will only send this message to one
> device. All other devices, that have sent a CONNECT message will get
> a RELEASE message as the indication, that they didn't receive the
> call in the end. So it's the job of the switch to make sure, that
> only one device is selected. These devices react with a RELEASE
> COMPLETE message and go back to the initial state (which is waiting
> for the next connection or a dialout by the user). See ITU-T Q.931
> section 5.2.9 "Non-selected user clearing" for details.
> 
> Does that answer the question?

It answers a different question to the one that Oliver Sturm
originally posed.  In the above, "device" is an ISDN device connected
to the S0 bus.  It did not become clear precisely what Oliver's
situation was, but it seemed to me that he either had a domestic 2B+D
line and a simple residential PBX that breaks that out to 8 POTS lines
(only 2 can have external connections simultaneously) , or he has a
30B+D PRI and a professional PBX that should be able to hunt on the
POTS side.  Either way, in his scenario, it is the PBX that needs to
arbitrate among POTS answerers, not the S0 bus among a number of ISDN
answerers.

-- 
Frank Cringle,      fdc@cliwe.ping.de
voice: (+49 2304) 467101; fax: 943357