Using many modems

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Hi,

On Thu, Nov 05, 1998 at 04:05:40PM -0500, Brian McGovern wrote:
> Multiple B channels on ISDN lines (either BRI, PRI, or E-1) do not get
> "Ring" at the same time. 

Uh, no B channel will get a RING at all.

The switch will send a SETUP (or was that ALERTING?) message on the *D*
channel, which all devices will get at approximately the same time.  This
is what will be reported as "RING".

In the US ISDN, devices can be tied to B channels, so if you have two
ISDN "Modems", you can distribute B channels "hard" to the devices.  In
Europe, this is very uncommon, and all devices and ISDN switches use
whichever B channel is available.

So, what happens is that one of the devices accepts the SETUP message
before the other one, and *this* device will get the call.  The other
will get something like "there is no call anymore".

Any real ISDN experts out there that can clarify this stuff better?

> The switch will select an active B channel that has
> been configured to accept an inbound call, and signal that B channel to go
> active. The device at the other end configured to use that B channel will go
> off hook. 

This is what happens *after* the D channel stuff has been done, and after
a device has been selected which will handle the call.

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