"trebor4258" writes:

I'm re-routing and adding some phone jacks in the house and found an oddity.


Since the alarm was installed, we have added DSL. And in case anyone is
particularly knowledgeable, the alarm box is a DSC PC1555.

[...]


The alarm guy's wiring is not CAT5, it's CAT3 or some other kind of station
wire and because of the routing, the circuit runs through it and the alarm
box before coming back to the telco box where it's spliced to my inside
wiring. That's adding about 100' of lesser quality cable before I ever have
a chance to get it to my modem.

The DSL signals are high frequency, so that "noise" is getting shot straight
into the alarm box and I see no kind of filter outside the box and no
reference in the box's manual about it having any kind of high frequency
filter.

Occasionally, we have problems with the DSL and I wonder if the alarm box
occasionally grabs the line to report in or just test itself. There's no
sort of filter around the alarm box for this either. If the alarm box comes
off hook, it has to "look" like a telephone and therefore it's presenting a
600 ohm load to the line across the entire frequency band. It think that
this is what the the "store-bought" DSL filters are supposed to prevent.
Maybe this is happening and causing out intermittent "outages". If the
alarm box is grabbing the line and doing what I suspect, then the house
outlets are effectively "dead" when it happens.

Has anyone else ran into this before and did it cause any problems?

Yes. I know some people who experienced periodic DSL dropouts due to
this.

My first thought is to tap the alarm guy's cable and grab what is
effectively the "first" presence of the telco pair inside the house to run
my additional outlets and put the appropriate DSL filters on the new drops
that I run. Secondly, I'd like to find out if there is any need for some
other kind of high frequency filter between the line and the alarm box.

The second best solution to the DSL problem is to run a separate loop
from the phone entrance to the DSL modem. That could mean moving the
modem to the entrance and running CAT5 to the computer/router. The
best solution is to get a "whole house DSL filter". The filter has one
"in" and a separate "out" for the DSL modem and a separate "out" for
the other phone stuff. Call whichever entity you think is most
responsible for the problem (alarm co IMO) and try to get them to fix
it for you. If that doesn't work, ask them where to buy an apropriate
whole house DSL filter.

Note that the whole house filter is a good idea anyway as it gets rid
of all the short wire stubs in the house and could conceivably improve
your DSL speed.

Bruce