DSL line stealing when there is no tone - DANGER - Operational content

Wed May 16 21:14:35 UTC 2001

At 04:46 PM 5/16/01, Greg Maxwell wrote:

>On Wed, 16 May 2001, Steve Schaefer wrote:
>
> > The main reason not to stick a tone on the DSL line is that the line
> > coding (2B1Q) used by SDSL uses the baseband (low frequency part of the
> > spectrum).
> >
> > For line codings that don't use the baseband (CAP, DMT and variants like
> > G.lite), the DSLAM (telco central office DSL equipment) is always set up
> > so that the DSL can be combined with a voice circuit over the same pair,
> > so it still doesn't put a tone on the line.
>
>I predict great profits for the first person to duct tape 100 'tracer
>tone-generators' into a 23 inch rack with 48v DC power source.

Better: a chip with a recorded voice: "This pair is in use" interspersed 
with a tone.

While present baseband signalling may be unable to handle such, it'd be 
useful if future ones purposely avoided the zero to 5kHz spectrum to allow 
for such a mechanism. Clearly the telco workers have demonstrated the 
absolute necessity for such a facility.
-----------------------------------------------------------------
Daniel Senie                                        dts at senie.com
Amaranth Networks Inc.                    http://www.amaranth.com