[Gllug] ADSL modem -- WTF?

Chris Bell chrisbell at overview.demon.co.uk
Thu Jul 15 13:36:47 UTC 2004

On Thu 15 Jul, Ian Norton wrote:

>  From my understanding of things, the adsl filters and simply high pass 
> and low pass filters, (low pass for phone and high pass for the dsl)
> the adsl signal must be modulated somehow as if it were a pure digital 
> signal it would have infinate (theoretically) frequency components, 
> also, if it were digital surely i could use isdn?
> correct me if im barking.
> Ian

   The current BT ADSL is similar to ethernet but with different headers,
controls, and much smaller packet size. The carrier frequencies used are not
the same as ISDN, and will so not work. The ADSL carriers are multiplexed on
top of the analogue phone line, and must be correctly separated from the
analogue and terminated to avoid signal loss, reflections, etc. I would
recommend the BT-style replacement front panel for the BT master box,
available from Solwise Ltd.


Chris Bell

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