Slashdot Mirror
France to Allow Cell Phone Jamming
ZuperDee writes "According to this article, the French industry minister has approved a decision to allow cinemas, concert halls and theaters to install cell phone jammers, on the condition that emergency calls can still get through."
No, GSM jammers of this type work by impersonating the local base stations by responding before them, but not actually letting anything through.
The systems have been available for a few years,
and are apparently very good at blocking out only a well defined area. The stumbling blocks have been entirely legal/regulatory.
I don't know if the available equipment handles it already, but there is no technical reason why the jammer couldn't engage slightly more thoroughly in the transaction and forward select calls.
sudo ergo sum
It could mean setting up your own "emergency calls only" cell in the cinema and blocking all other frequencies. If this were the case, your phone would 'roam' to the cinema network and patrons would make emergency calls through that. It would be very expensive for the cinema to shoulder the cost and possibly have some interesting legal repercussions.
It does in some ways : we can suspect that the concept is accepted but still requires realisation.
I guess it'll imply some switches set in send only mode along with possible dial limitations (in France, emergency numbers begin with 1, the others begin with 0).
Trolling using another account since 2005.
It is possible, although not as simple. First put a lot of metal in the walls and ceiling to block all radio signals. (cell phones are nothing more than advanced radios)
Then put a small cell phone tranceiver (a small version of those cell phone towers) inside the room and program it to only allow outgoing calls to the emergency numbers (e.g. 911).
Is it really necessary to be reachable while you're at the cinema ? No. And if it is necessary, you shouldn't be at the cinema.
- Leon Mergen
http://www.solatis.com
The only thing that comes to mind is having a special node at the theatre thats essentially a repeater (but doesn't ring the phone or allow outgoing calls to be made). Calls to anyone with a phone from a certain prefix or list of numbers (given to any emergency responders) is allowed through. Think of it like a cell-phone firewall.
If that's how they're planning on doing it I don't know. But there has to be some way of distinguishing emergency calls, or emergency cell phones from normal everyday calls/phones.
AccountKiller
However networks in the same country might stop customers from competing networks inadvertantly roaming onto their own. I doubt this is out of malice, but is seen as way to prevent the hell that would result from millions of phones winking in and out of each other's networks and furious calls to customer service.
But even so, networks do allow roaming for "Emergency calls only". Your phone will say as much when it can't find it's own network. In other words, you can still dial an ambulance.
I'm not au fait with GSM protocols but I assume that the network says what services it supports when you establish the link, with emergency (outgoing calls) service being the most basic. I also expect that very few GSM operators block any mobile user from this service. Even a deactivated SIM in an old phone can often make emergency calls - something worth trying out before tossing a phone.
So I don't see any issues here. The phone's regular network might be missing (because it is jammed), but the phone will see the "cinema" network and it will start using it. The phone is unlikely to not work when the only network it can find offers some service even if it is emergency calls only.
According to the news on French tv, people such as doctors will be able to receive calls (if ask for it) and everybody will be able to call outside
Don't Tell Me What I Can't Do!
This law passed not just for movies. Theaters, concerts, Opera, every public artistic performance falls under that law: They are now allowed to jam cell phones.
Write boring code, not shiny code!
The grandparent poster has reading problems or doesn't know what the word "and" means.
There's actually two factors at work here - digital cell phones attenuate their transmit power level based on the strength of the signal they receive. The theory is that if they are receiving a strong signal from a cell tower, they must be very near it physically, so they don't need to use as much power to transmit and be heard by the tower. So the first thing they do is set up a local base station; all the phones will lock in on it because it is the strongest signal around, and they will all reduce their transmit power because the local signal is so strong. So this automatically means your phone will only use the local base station, no other cell towers will be able to hear the weak signal your phones will be putting out.
The region being affected is easily controlled using directional antennas. Most cell towers already use a 120 degree beam spread, so directional antennas are the usual already, but they can certainly use a narrower beam antenna if they want.
As for routing emergency calls, again, the network tells the phone what the phone is allowed to do. No problem there...
-- *My* journal is more interesting than *yours*...
Trivial. The same way that you handle calls in a large shopping mall or other localised concentration of people. You setup a micro-cell. The difference is the one in the cinema will only route emergency calls; the rest get a recorded message saying "fuck off you sad bastards: try watching the film." QED.
Bad analogies are like waxing a monkey with a rainbow.
I live and work in Toulouse, and I was somewhat surprised at this article - there already are phone jammers operating in cinemas here, possibly illegally?
;-)
It's a good idea though, there is no need to have a mobile phone when watching a film
You can control the affected area even more precisely than that: if you have two or more antennas, you could triangulate the position of a phone and choose whether to service it or not based on its position. Meaning that you can literally draw your block-zone on the map and when you step outside that invisible line, your phone works. (Not sure they actually do, but it's certainly possible.
This also means you don't have to drown out any other transmitters, you can just play man-in the middle: you know which phones are in your zone, if a tower tries to contat it, you say you're it, but can't answer. If a phone tries to contact a tower, you pretend you're it an denies service. All you have to do is be first.
Combined, you have a very robust soloution with a well-defined virtual cage that is "invisible" from the outside but completely "dark" on the inside.
sudo ergo sum
A lot of people are missing the point.
Emergency calls OUTSIDE, people.
RTFA man, it says
"Devedjian specified however that emergency calls and calls made outside theaters and other performance spaces must not be affected."
It says nothing about emergency calls OUTSIDE.
You'll have that sometimes...
And what did these same people do before mobile phones?
Pagers, or backup staff on-call. You should not have been responsible alone for a system like traffic control 24/7, everyone should have some time off.
Doctors are not on call all the time, when they are, they have to avoid situations like this.
I think that this is great. I'm a classically trained musician and a sound engineer so I spend a lot of time either performing or recording concerts. When I'm onstage, I'm already a bundle of nerves and have to concentrate like hell for fear of messing up. Whenever I hear a phone go off, it is very distracting. I can ignore it and carry on, but it does throw you for a moment. 99% of the time it won't result in any audible wobble, but if it happens at the wrong time it can throw you completely and you screw up bigtime. When I'm recording, it is even worse. Even if somebody has their phone on silent but are sitting close enough to some of the gear, you can get the lovely du-du-du-du, du-du-du-du, du-du-du-du-duuuuuuuuuu sound captured in your recording. Again, this happens very rarely, but when it does I have to be physically restrained... I also lecture at a university - whenever students use their phone in class, it shows a distinct lack of respect for me and for the other students, some of whom are finding it difficult enough to follow the course content as it is.
Is my phone the only one on the planet that has "Vibrate, then ring"? I get 3 rings of time (about 10 seconds or so) to look at who is calling and answer or push them to voicemail. If I'm not wearing my phone (it's on my dresser at night, for example), I'll hear it after the first 3 rings.
Honestly, I can't why more people don't use that:
I NEVER have to adjust my phone for any situation. Which is good because I'm insanely forgetful.
faraday cage in the theatre, and a GSM picocell that only routes emergency (i.e. 911 or 112 in Europe) calls going OUT to the emergency services - everything else blocked. This is pretty easy: the same thing is effectively happening (albeit without the trivial faraday cage - an earthed liner of chickenwire behind the wall coverings will do this) everytime your GSM phone says "SOS calls only" on the display - it's telling you there's a GSM network nearby, but (usually because your phone provider doesn't have a roaming agreement with that network provider) you can't use it, bar emergencies.
Think of others for a change. Some people have hearing aids, and mobile phone calls interfere with them, even when the phone is set to vibrate.
Also, you run the risk of having your face punched in if your phone rings. You won't be much use if you are in a hospital bed yourself.