Out of respect to this OP I’m starting a new thread.
I realize there are many parts of the US where it’s illegal to employ a cell phone blocker in public. But is it ever illegal to block cell traffic within your own home?
How narrow can these devices make the blockage? Is it automatically a 100 yard radius, or can I narrow it to the room I’m in?
Apologies if it’s an easy search, but it’s not one I’m going to try from the work computer. 
(Bolding mine.)
I’ve been in a couple of locations where my signal went from full bars to the SOS signal, meaning that I could only make 911 calls and nothing else. What sort of device does this? Is it considered a jammer as well?
Bolding different parts than what Duckster did:
Since the question is specifically asking about using blockers within a home, I don’t think this quote answers the question.
There is surely also a significant difference between passively obstructing the signal by, say, turning your house into a Faraday cage, and actively jamming the signal.
I’ve never seen an SOS signal on the cell phones I’ve owned and I can’t imagine that it’s possible to selectively block regular calls while allowing 911 calls to go through. Perhaps you were in a location with a very weak signal?
The OP in that thread absoltuely did not want to jam the sgnals around her dinner table to foil her children’s texting tricks.
What I want to know is, is it phycially possible to jam just a small area, and also is it legal? I know service is jammed inside our local hospital, but it’s big enough to leave room for doubt.
I’d swear I once heard about a church? getting in big trouble for blocking cell signals. And it wasnt even on purpose. The metal roof or a giant metal cross or something like that was causing problems. And I am pretty darn sure I heard about it here.
I am not aware of anyplace where it is illegal to block cell phone signals inside of a private residence using purely passive measures (i.e. a Faraday cage). The same is not true of publicly accessible locations, like a theater or a church.
Using active jamming devices though is a whole different ball game, and those come under the jurisdiction of the FCC. Generally speaking, using jamming devices of just about any sort is illegal. I don’t know enough about the details of the FCC’s waivers, exceptions, etc. to say under what circumstances they would allow it.
My phone says “no service” (with bars) instead of “no signal” (no bars) when it is within range of a cell system that it is not authorized to access. In those circumstances I would be able to dial 911 but not dial a normal phone call.
Exactly what your phone displays may vary. Not all cell phone service providers are required to provide service for all types of cell phones, so you can sometimes end up in an area where your particular phone may be able to reach a service and not be authorized to use it. The providers are however required by law to let you dial 911 on their service.
My understanding is it is illegal to block signals without the FCC’s prior approval. Installing a device to block signals is a no no. Constructing a room or building that blocks cell phone reception is a greyer area that can come down to an argument of design and intent.
FCC restrictions apply even to private residences.
If you decided to jam a room in your house anyhow I doubt you’ll find anyone that figures it out unless you go around telling people and even then the FCC has better things to do then worry about what you do to your kitchen. If you’ve set up a murder room in your basement and block out cell phone reception just in case a victim sneaks a phone in, when they catch you maybe they can add a FCC fine on the list of charges, the least of your worries.
To expand on engineer_comp_geek’s comment:
A cell phone tends to support multiple ‘bands’ - different ranges of RF. Not all carriers use the same ones. It’s theoretically possible to block the ones you are using, so your phone loses contact with the preferred carrier. If they don’t have a roaming agreement with another carrier that is on a different band, you would camp in SOS mode.
-D/a
OK. That makes sense. I’ve only ever had ATT cell phones and never experienced this.
Really? Any cites at all that passive measures (like metal or mesh walls) would in any way violate the law? I would be surprised if the FCC can dictate architectural standards, other than forbidding a prohibition against dish antennas on condos.
FCC regulates radio broadcasts; to jam a cell service you would have to broadcast on a reserved frequency. The smart ones simply pretend to be a cell tower but don’t do anything with your call; the dumb ones just blast away to disrupt service, and it would be hard to make something like that which would not leak out into public space (even if not loud enough to really block traffic)… Unless you put your jammer in a Faraday cage.
I think that you’d need to define device to paint a complete picture. In this context, I don’t think that passive blocking would qualify as a device. If it did, wouldn’t an elevator or aircraft where you lose signal be a device?
I’m not aware of any laws specifically banning passive devices like Faraday cages and RF shielding, but it is my understanding that if you intentionally block cell phone use in a publicly accessible place like a church or a theater that you open yourself up to lawsuits for basically creating a safety hazard (can’t dial out in an emergency). Seems kinda silly to me, but this is the land where you can sue McDonalds because hot coffee is hot, so there you go.
Unintentionally blocking cell phone signals though (like installing a metal roof) is perfectly acceptable though. It’s the “intentional” part that can get you in trouble.
IANAL. This is just my understanding of it.
It’s rather difficult to prove ‘intent’ in court, though.
P.S. My stucco house, with wire mesh underneath, does a pretty good ob blocking cell phones (and Wi-Fi). Was that the intent of the builder? In 1909, about a dozen years after Tesla filed his p[
atent for radio?
It’s been a few years ago. There was one theater that when you entered it, would switch to SOS calls only. The theater closed a few years ago. I’ve also been in a few museums where this was the case as well. The signal was very strong and as soon as I stepped out of the building and maybe a 20 or 30 yards away, the normal signal would come back.
A somewhat similar situation to what others have described. My service is with T-Mobile. T-Mobile and AT&T are compatible, in that they use the same system, but I am not authorized to use AT&T. So if I’m in an area where the phone can’t find any T-Mobile service, but it does find AT&T, it will display the SOS symbol.
Worse, emergency responders on the inside can’t get calls that summon them to respond to emergencies. What, you think everyone responsible for saving lives in a hospital setting is sitting around in a hospital 24 hours for the 1/3 of the year they’re on call?
Certainly, if it’s hot enough to cause third-degree burns and McDonald’s knew it.
And you can demonstrate their cost-benefit analysis showing that they totted up the danger to their customers and decided that the savings of $.03 or so per pot by using hotter water and therefore slightly less coffee grounds would outweigh the likely losses in lawsuits by the injured customers.
I get so sick of hearing that one brought up as an example of absurd lawsuits. What McDonald’s corporation did there was horrible, and people should have gone to jail for it. The best we could hope for was that the courts would award enough damages to make other companies take heed and rank customer safety a bit higher in the scale. Given that you have to ask for an extra hot cup at Starbucks, I’d say it worked.