Jamming devices silence mobiles

In order to cut off mobile phones, jammers emit low-level spurious signals on the radio frequency bands used by the operators (900 and 1800 MHz). Once a jammer is in service, any link between the phones and the base stations of the cellular network is cut off. For mobile users in the jamming area, everything happens as if the place was not covered by the network of their operator. No nuisance ringing: Incoming calls are automatically directed to voicemail. No outgoing call is also possible.This basic principle is added some variants depending on the type of jammer. In a preliminary classification, which foreshadows the complexity of the next interference rules and limitations, ART has identified six categories of aircraft. First, there are those who emit “noise” continuously on the frequency bands concerned. These do not make any detail. In their coverage, the jamming is continuous and no mobile works. Then there are devices that emit waves only when they detect an active mobile (on). More subtle variant: those who activate only when the mobiles are about to communicate.

Selective jammers

These two selective scrambling techniques make it possible to limit the electromagnetic emissions of which we still do not know if they are safe. There are also smart devices that communicate with mobiles and send them messages to switch to restricted mode. With these models, call and receive restrictions can be adjusted on a case-by-case basis (for example, to allow , emergency calls). Finally, there are more complex jammers who communicate with the base stations of the network, either to lure the mobile or to request a filtering service from the operator. The coverage area of ​​the jammers depends on a large number of factors. technical as environmental: transmission power, type of antenna used (directional or not), placement of the device, distance from the jamming zone to the cell relay, presence of active obstacles … The maximum distance of effectiveness from the place where the cell phone jammer is installed varies from a few meters for the pocket device, to several tens of kilometers for models for military use.If these are obviously not marketed to the general public, jammers personal, they begin to leave confidential circles of amateur counterintelligence. It is not difficult today to find mail order models on the Internet. First prize: around 180 euros (less than 1,200 francs), taxes and delivery fees included, for a compact model that scrambles radio broadcasts within a radius of ten meters. For an autonomous device, transportable and compact (the size of a mobile), count about 800 euros (5 247 francs). Remember: the use of these devices is prohibited in France. But it is apparently possible to get some without showing white paw. The arrival of private jammers in theaters, even if it will probably be subject to strict rules enacted by the ART, poses several problems.

Problems in perspective

First, who will actually have the right to use them? If the law seems clear, its interpretation can lead to some overflows. In addition, the new legislation creates, in fact, voluntary hedging holes in the networks. If the interference is incorrectly confined to the perimeter of the theaters, it may affect the quality of service in the neighborhood. The law also requires mobile operators to route emergency calls (such as the 112, European emergency number). In the scrambled zones, this obligation can not be respected if the jamming devices used block indiscriminately all the calls. For the public, does this mean that there will be safer cinemas or theaters than others? Until the installation of the first devices by the room operators, these questions may have been resolved. In the meantime, it is always possible to make or receive a call during a show. But be smart: turn off your mobile