[Asterisk-Users] Ring more than two isdn phones simultaneously

[Peter Svensson]

On Sat, 20 Aug 2005, Nico Giefing wrote:

> how many connection do you have from your asterisk to the old pbx?
> 
> i think on 1 ISDN connection its only possible to let 2 phones ring, because
> 1 ISDN 2 channels...

This is a limitation in Asterisk, not ISDN. Asterisk reserves a B-channel
for each destination at the time of the CONNECT message. In the isdn world
it is common to not actually allocate a B-channel until it is needed to
carry audio. This also prevents Asterisk from letting the upstream switch
select the B-channel on outgoing calls to the pstn.

Asterisk is written this way since it uses the audio channel as the 
fundamental unit, with the D-channel as carrier of signalling for the 
individual B-channels. Another way to view ISDN is to consider the 
D-channel the fundamental unit, which can carry several audio streams as a 
side effect of the signalling. The first viewpoint resembles the 
traditional view of telephony as individual circuits, the second resembles 
the ISDN/SS7 view of the world.

Changing Asterisk to be more ISDN-like is quite a lot of work. 

Peter

> 
> ----- Original Message ----- 
> From: "Arik Funke" <arik.funke at gmx.de>
> To: <asterisk-users at lists.digium.com>
> Sent: Saturday, August 20, 2005 7:44 PM
> Subject: [Asterisk-Users] Ring more than two isdn phones simultaneously
> 
> 
> > I am using a HFC-S card in nt mode with zaphfc driver to connect an
> > internal isdn bus. I would like to signal an incoming call on, let's
> > say, 4 phones. Right now I use:
> >
> > Dial(Zap/g1/21&Zap/g1/22&Zap/g1/24&Zap/g1/23&Zap/g1/29,,t)
> >
> > where g1 are my two isdn channels provided by HFC-S card an the
> > 21,22,etc my internal numbers.
> >
> > When the command is executed however, only the first two specified
> > phones ring. Etc. with the first channel 21 ist called, with the second
> > 22. How can I get asterisk to signal to all phones with just one isdn
> > channel? I am trying to duplicate the setup I had with my old isdn pbx
> > with did above trick just fine... Maybe somebody can help me configure
> > asterisk appropriately?
> >
> > Cheers,
> > Arik
> >
> >
> > PS: I gave following a try but without success:
> > Dial(Zap/g1/21-29,,t)
> > Dial(Zap/g1/21+29,,t)
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Peter
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