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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
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
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 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.