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

Steve Schaefer schaefer at simone.dashbit.com
Wed May 16 20:10:11 UTC 2001

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

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.

On Mon, 14 May 2001, Alex Bligh wrote:

> > as for relibility, I cant tell you the number of times a Verizon tech,
> > would be out to install a phone line and steal one of our dsl lines cuase
> > it did not have a tone.
> As a (serious) question, why not stick a tone on it? How much
> can an oscillator at the CO plus some trivial passive low pass
> filters (one set per line), cost? (Or, if you aren't the DLEC,
> stick it at cust prem). Just don't use the trace tone... (translation
> to US terminology may be required)
> --
> Alex Bligh
> Personal Capacity

More information about the NANOG mailing list