Google Answers Logo
View Question
Q: Blocking cell phone reception ( Answered 4 out of 5 stars,   3 Comments )
Subject: Blocking cell phone reception
Category: Science > Technology
Asked by: pensacola-ga
List Price: $20.00
Posted: 11 Oct 2004 20:51 PDT
Expires: 10 Nov 2004 19:51 PST
Question ID: 413500
I have a single story medical office, and would like to block cell
phone reception in the exam rooms.  I suspect active methods are
outlawed by the FCC.  Is there a passive way to do this? (ie, install
metal panels above the ceiling tiles).  If so, is it legal?  No matter
how many signs are placed, people will continue to receive calls at
the worst times.
Subject: Re: Blocking cell phone reception
Answered By: redhoss-ga on 12 Oct 2004 09:40 PDT
Rated:4 out of 5 stars
Hello pensacola, I enjoyed researching your question and have found
some material that might help you. First, you are correct active
blocking is illegal:

The operation of transmitters designed to jam or block wireless
communications is a violation of the Communications Act of 1934, as
amended ("Act"). See 47 U.S.C. Sections 301, 302a, 333. The Act
prohibits any person from willfully or maliciously interfering with
the radio communications of any station licensed or authorized under
the Act or operated by the U.S. government. 47 U.S.C. Section 333. The
manufacture, importation, sale or offer for sale, including
advertising, of devices designed to block or jam wireless
transmissions is prohibited. 47 U.S.C. Section 302a(b). Parties in
violation of these provisions may be subject to the penalties set out
in 47 U.S.C. Sections 501-510. Fines for a first offense can range as
high as $11,000 for each violation or imprisonment for up to one year,
and the device used may also be seized and forfeited to the U.S.

Passive blocking is not illegal yet, but that could change in the
future. Also, there are many illegal jammers in use:

Mobile phone signal jammers are illegal in the US, but that doesn't
mean they're not used. They're apparently increasingly common, and are
expected to spread quite a bit in the near future. The FCC says that
using a jammer is considered "theft" of airwaves, because that
spectrum has been allocated as property to a commercial entity. The
writer of the article wonders, though, about "passive jamming" - such
as putting up buildings made of material that block out cell phone
signals. While some don't like the idea of having their signals
blocked - others think it may become a lot more popular in the future,
if only to have areas to "disconnect". The article points to the rise
of camera phones as a "bottom up surveillance society" as a reason why
we might want areas that have no signal. That makes little sense to
me, since anyone using a camera phone can still snap the picture, and
then just upload it later when they're in range of a signal. Still, it
will be interesting to see if anti-jamming equipment becomes popular.
Most people have no idea if a jammer is being used, since it just
looks like there's no service. This makes it very difficult to figure
out if someone is using a jammer, and means that no one's getting
caught using these things right now.

In this same article I found this interesting claim:

Block, don't jam, and be legal 
We wish we could build powerful jammers that would stop cellphone use
in restaurants, theatres, even around where we are driving, and while
technically possible, these devices are quite illegal in the US. There
is a way to stop some annoying cell phone use that is legal, however,
and that is to block the signals from ever getting to the cell phone.
Blocking is legal because it is just shielding and doesn't interfere
with any users external to the shielded areas. Hospitals, aircraft,
even Dunkin Donuts, can be shielded with simple metal structures that
are designed to enclose the signals from or to the cell phone. We have
developed a simple, passsive and legal shielding system that can be
used to block signals at certain times, such as during an
intermission, or at a meeting break.

For further information, visit
-- Bob Crowley

AMBIT Corporation's Antenna Distribution technology is uniquely
designed to conduct wireless signals from place to place in
RF-sensitive environments where control of radio frequency energy is
required. Our ability to collect and route cellular and other personal
communications device signals within a closed environment allows safe
and regulated control in RF sensitive settings such as commercial
aircraft, hospitals and in buildings. Some features:

I found many references to a paneling material developed in Japan, but
can find no sources to buy it:,0,3510198.story

Japanese researchers are developing wood paneling infused with
magnetic metal to prevent cell phones from ringing in movie theaters,
concert halls, restaurants or other venues where they annoy patrons.
The goal of Hideo Oka and a team of engineers at Japan's Iwate
University is to find a blocking method that is inexpensive and easily

They have experimented with four ways to combine wood and magnetic
metal particles to produce paneling that absorbs radio signals. Their
aim is to create a process using recycled metal and wood materials so
that the paneling could be sold cheaply at hardware stores.

Here is what sounds like a good inexpensive method to block cell phone
signals from a room or building:

  Simple - mount steel mesh or chicken wire around all your walls,
cover them with decorative wall board, and run a wire down to a good
electrical ground, such as conduit pipe or water pipe.  This will
effectively block incoming or outgoing cell phone transmissions. After
all, it is YOUR  office or store, right?  People can go outside to
make calls, as they should.

I wanted to confirm that this would actually work and found this:

When you build or do any extensive renovation you are probably going
to use a lot of drywall. If you do install a few layers of chicken
fence or other suitable fine grid or wire. Make sure the doors are
metal (fire code I would think) and that they maintain a good contact
to the grid etc etc etc. When the doors are closed you are not going
to see an increadable ammount of attenuation to any RF signals with a
wavelength longer than the mesh pitch and a good attenuation to most
everything else.

Here is a simple solution to protect your existing windows:

Don't want to replace the whole window to get good shielding? This UV
protected aluminized Mylar thin film is specially designed for window
applications and provides certified 99% shielding at cell phone (900
MHz) frequencies without the hassle of grounding. Reduces glare and
the fading effects of UV with good light transmission. One side has a
mirror-like finish, the other side has a bluish tint. Apply it to the
inside of your windows with either side facing out according to your
aesthetic preference. Use tape, spray adhesive, staples, tacks or just
about any other method to hold it in place. Easy to trim to size with
scissors or blade. The perfect complement to shielded walls. Generous
60" wide.

If you want to take the chance of being caught and prosecuted, here is
a good source for jammers:

Cell Block Technologies Inc. develops, manufactures, and markets
products that provide cell phone / mobile phone privacy by creating
wireless communications-free areas.

Cell Block Technologies? products and services address the issues of
unwanted use of wireless communications technology for  Security,
Safety, Privacy and Productivity.  Our principal product line can
detect and control the use of cell / mobile phones within limited

The Company?s primary global markets consist of Prisons, Religious
Institutions, and Foreign Embassies.

Other markets have been identified to include the petroleum,
healthcare, hospitality and entertainment, banking and transportation
industries, as well as private individuals.

Because GSM is the single most important cell phone and mobile phone
protocol in use today, the Company's early products are GSM-based.

Cell Block Technologies? principal product line consists of Quiet Cell
silencing products.  Quiet Cell silencing products can detect and
control the use of cell phones / mobile phones within limited
restricted areas.

The cell phone / mobile phone silencer system redirects incoming calls
to voicemail and blocks outgoing calls.  The system is not a
traditional cellular phone jammer.

Cell Block Technologies, Inc. offers the only cost-effective,
non-jamming, extensible solution to address the problems posed by cell
phone / mobile phone and other wireless communications technology.
The Company expects to provide early products in the 2nd half of 2004.
 Specific delivery dates are dependent upon additional external R&D

There are many discussions to be found on the web both pro and con on
cell phones. There are very strong feelings on both sides. It is
impossible to predict where future legislation may lead and what is
legal or illegal today can change very quickly tomorrow. I hope that
the info I have given you is helpful and informative.

Down with cell phones, Redhoss
pensacola-ga rated this answer:4 out of 5 stars

Subject: Re: Blocking cell phone reception
From: wifi_jaxwireless_com-ga on 11 Oct 2004 21:26 PDT
Hey ,,,

 I am in the Jax Fl area .. Not too far away..
Interesting question.8) 
... I am a private investigator here.

Check the page.

Now keep in mind that this will stop transmission/reception of cell
phones BUT only specific frequencies are blocked. IE Cell phones. So
any other kinds of transmission equipment could leave the building....
Say to ... the parking lot.

Thanks Steve
Subject: Re: Blocking cell phone reception
From: barnacle_bill-ga on 24 Feb 2005 03:11 PST
just a thought... wouldn't this also block Wifi traffic?  this is an office, right?
Subject: Re: Blocking cell phone reception
From: barnacle_bill-ga on 25 Feb 2005 01:44 PST
If this could block Wifi traffic, the chicken wire not the cell phone
blocker... it could seriously cut the possibilty of Wifi hackers?
anyone else got any ideas on this?


Important Disclaimer: Answers and comments provided on Google Answers are general information, and are not intended to substitute for informed professional medical, psychiatric, psychological, tax, legal, investment, accounting, or other professional advice. Google does not endorse, and expressly disclaims liability for any product, manufacturer, distributor, service or service provider mentioned or any opinion expressed in answers or comments. Please read carefully the Google Answers Terms of Service.

If you feel that you have found inappropriate content, please let us know by emailing us at with the question ID listed above. Thank you.
Search Google Answers for
Google Answers  

Google Home - Answers FAQ - Terms of Service - Privacy Policy