1
Blocks out radio-
frequency interference
from your telephone
lines.
One- and two-line
models are available.
Choose from four
different frequency
ranges: LF, HF, VHF,
and UHF.
To eliminate severe
interference, install
one filter on a line and
another filter right
behind the first one.
T
elephone interference happens
when your telephone picks up
external radio frequencies and
mistakenly decodes them along
with the real telephone signal.
Your telephone’s own cord can be
its worst enemy, acting as an
antenna to pick up unwanted
radio signals. It’s worse than ever
in modern telephones, whose
solid-state components make
them susceptible to even the
slightest levels of radio-frequency
interference (RFI).
The interference can come
from any radio source—broad-
cast radio stations, cellular
phones, even copiers or fluor-
escent lights. Not only does it
make conversations noisy, but it
can also play havoc with other
devices that use the phone
lines—scrambling modem data,
You don’t have to put up with noise on your phone lines.
It’s surprisingly easy to get rid of almost any interference.
Key Features
RF LINE FILTERS
accidentally triggering an
answering machine, or corrupting
a fax.
There might be more inter-
ference on one phone than on
another in the same building—
specific radio waves reach differ-
ent places, and various phone
designs are affected differently by
the interference.
Can you get rid of RFI? Almost
always. All it takes is a little work
diagnosing the problem and the
right RFI filter combination.
Diagnosing the Problem
If you’re having trouble with
interference on your phone, be
observant. Is the problem con-
stant? Is it the same on all exten-
sions on the same line? Does it
change when you change any-
thing on the line—when you add
or remove a phone, for example?
Looking for Bad Phones
The first thing to check is
whether it’s your phone that’s
causing the problem. Modern
telephones, with their solid-state
components, are especially sus-
ceptible to RFI. And a telephone
might easily keep on working
even with a malfunction that
causes interference to other
phones on the line.
If you have two or more tele-
phones, try this test to find out
whether telephones connected to
your line are adding interference:
1. Make sure all the phones
are “on hook” (hung up).
2. Pick one phone where you
can hear the interference.
We’ll call this the “control
point.”
3. Unplug all the other phones
and any equipment con-
Black Box Corporation
• 1000 Park Drive • Lawrence, PA 15055-1018 • Tech Support: 724-746-5500 •
www.blackbox.com
•
e-mail: [email protected]
© 2005. All rights reserved.
Black Box Corporation.
8/5/2005
#17099
