[PLUG] DSL Issues

Michael Barnes barnmichael at gmail.com
Thu Mar 21 18:46:02 UTC 2019


Not really Linux related, but you're the best group I know to ask this.

I haven't dealt with DSL for some time. One person I help out recently went
back to Century Link DSL from satellite. When I dealt with DSL years ago,
the phone line ran to the modem, then from the modem to other phones in the
house. If you went to a phone that didn't go through the modem, you needed
a filter. In this installation, the existing house wiring consisted of odd
collections of non-telephone wire, including thermostat wire, doorbell
wire, and other unidentified stuff. Although it worked, the bandwidth was
atrocious with speeds barely at dial-up service. There were no filters in
the system, but I did not hear the expected "DSL buzz" on the other phones.
I installed a new run of CAT6 cable, using one pair for the line from the
Century Link interface box to the modem. Surprisingly, the modem would not
lock on to the DSL. I had used a cheap RJ-11 jack labeled CAT3, which
turned out to be the problem. When I replaced the jack with a CAT6,
everything locked in and we had 3+ mbps of service.

So, my questions are, first, does today's DSL use a higher frequency signal
that no longer needs filters to prevent it from being heard in other phones
on the line? Also, if that is the case, would some cheap Chinese CAT3 jacks
somehow block or distort the DSL signal, preventing the modem from
detecting it? Through exhaustive DC continuity testing, I determined
everything was wired correctly and polarity was proper. The analog phone
signal worked just fine. It was all very perplexing.

Thanks for any insights to this.

Michael



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