In the United States and South America, most digital mobile phones operate on the 1.9 GHz band, while most of Europe and Asia use the 900 Mhz and 1.8 GHz bands. Even if your phone operates on multiple frequency bands, operation on a single frequency band is sufficient to cause call failure by interrupting outgoing calls or incoming voice data.
Mobile phones are usually used in prisons, but these items are illegal in US federal prisons. The prison uses gsm jammer to block calls, thereby preventing the coordination of gang-related activities within the prison and preventing unauthorized communications with the outside world.
GSM/CDMA network killer jammers also provide security during transportation by senior officials. The US presidential motorcade used these devices, and cell phone jammers played a role in thwarting the 2003 assassination of Pakistani President Musharraf. Mobile phones are a common trigger in improvised explosive devices, and sometimes jammers are used to prevent explosions.
In France and Japan, it is legal to use GSM jammers in movie theaters, art galleries, concerts and other public places.
The French Ministry of Education is planning to introduce GSM jamming devices to prohibit students from using mobile phones in schools. China has begun to use jamming devices to prevent students from cheating. Japan also cited jamming devices to prevent students from cheating in exams.