[Gllug] [slightly ot] ADSL config fun

John Winters john at linuxemporium.co.uk
Fri Sep 20 08:01:42 UTC 2002


On Thu, 2002-09-19 at 23:28, Chris Bell wrote:
> On Thu 19 Sep, John Hearns wrote:
> > 
> >
> > 
> > Thinking about all this - I guess that's why ISDN and ADSL service can't
> > exist on the same pair of wires? Or am I wittering again?
> > 
>    I thought that the reason why the BT attempts at ISDN and ADSL do not
> coexist is that the local ADSL carrier frequency is not the same (lower?).

This topic has been discussed a lot in uk.telecom.  The conclusion
reached was that you can have ADSL+POTS or ADSL+ISDN but if you have
both in the same bundle of wiring there is interference between them. 
In Germany, where they are far more advanced than us at upgrading from
POTS to ISDN the norm is ADSL+ISDN.

It's always puzzled me why they don't go the whole hog and just make the
connection ADSL, then piggy-back any required voice circuits over it.  I
have a point-to-point DSL connection and each of the DSL boxes has a
telephone socket on it in addition to the Ethernet one.  When I use the
telephone circuit it just steals about 48k from the data connection. 
You could easily piggy-back one permanent ISDN D channel over the ADSL
connection, then snaffle bearer channels as needed.

John

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