Telecommunications Tech Blog May 2014
Odd Problems with Data Noise on IP Office Systems (and
Both Noise you Can Hear and Noise you Can't Hear!
By Mike Sandman •
I've been hearing about a lot of odd
problems occurring on Avaya's IP Office systems connected to fake phone lines
from cable companies and VoIP stuff, and even sometimes on real copper POTS
The symptoms seem to be different at
different premises. It probably depends on the brand / model of the box the
cable or VoIP company put in? Or how the phone company delivers the copper POTS
lines (the data noise may be induced from other pairs in the cable)?
The bottom line seems to be that the
cable company and VoIP boxes that try to make POTS lines tend to put out a lot
of data noise above voice frequencies. The engineers who designed these
boxes didn't think the data noise would make any difference on a phone or phone
system Trunk / CO line so they didn't think about it. But you get to fix the
problem they created.
This noise causes really strange
things to happen on some phone systems - both odd operation that effects the
processors in the system, and noise that you can hear (probably a harmonic of
the data noise?).
You probably can't hear this data
noise on a butt-set since the noise is common mode (the same on the tip and
ring), and your butt-set has no reference to ground like a phone system does
through AC power.
KSU-less phone systems are almost
universally effected by this noise because it's right at the same frequency the
KSU-less manufacturers use to communicate between their phones, usually above
the voice frequency on Line 1 only.
So far, our Data Noise Filters
seem to be solving the problems if they're placed in-front of the phone system -
either at the cable box (which is the right place for a KSU-less system) or at
the KSU / PBX.
We make RJ-11 and RJ-14 (2 line
modular) versions of the Data Noise Filter, and a 1 Pair Hard-Wire
If you have modular jacks on the cable
or VoIP box, or on the phone system, it will be easy to just
plug in the Data Noise Filter on the line(s) from the cable
or VoIP box to see if it helps. If it doesn't fix your
particular problem you can take it out and try it on the
On a KSU-less system you probably only need the filter on
the first line... BUT you must put it at the cable or VoIP box - not between the
phones! If you put it in-front of a phone it will block the data sent between
the phones, and you won't have lights, hold, intercom or other features.
We can make an RJ-45 version, but you can't use
that by putting one in-front of each KSU-less phone, so there's probably no
need for it.
It's a good idea to keep one in your
truck. There's no way to know if it will fix a particular symptom without trying
it! On an IP office, you might want to disconnect the lines without the Filter,
since just putting it on one line wouldn't prevent the data noise on the other
lines from screwing up the system. If it fixes the problems on the one line, you
can get more to fix the whole system.
To read more on data noise problems,
and to see where to place the Filters on KSU-less systems, see our Data Noise
Elimination Tech Bulletin: