Cell phone jammers have both benign and malicious uses. Police and the military often use them to limit or disrupt communications during hostage situations, bomb threats or when military action is underway. Portable personal signal jammer are available to enable their owners to stop others in their immediate vicinity (up to 60-80 feet away) from using cell phones.
To jam a cell phone, you need a device that broadcasts on the correct frequencies. Although different cellular systems process signals differently, all cell-phone networks use radio signals that can be interrupted. GSM, used in digital cellular and PCS-based systems, operates in the 900-MHz and 1800-MHz bands in Europe and Asia and in the 1900-MHz band in the United States. Jammers can broadcast on any frequency and are effective against AMPS, CDMA, TDMA, GSM, PCS, DCS, iDEN and Nextel systems.
High security premises, such as prisons and detention centers, can also benefits from a cell phone jammer because it can prevent illicit communication between inmates and visitors.
Of course, a cell phone jammer can also be beneficial in places such as a movie theater or a library where other patrons expect silence so they can enjoy their activities.
Jammers are usually undetectable, and users may experience minimal effects such as poor signal reception. Jamming devices may be used in any location but are typically deployed where cellphone use may be disruptive, such as in libraries and restaurants.
Jamming devices overpower the cell phone by transmitting a signal on the same frequency and at a high enough power that the two signals collide and cancel each other out. Cell phones are designed to add power if they experience low-level interference, so the jammer must recognize and match the power increase from the phone.
Cell phone jammers have both benign and malicious uses. Police and the military often use them to limit or disrupt communications during hostage situations, bomb threats or when military action is underway. Portable personal jammers are available to enable their owners to stop others in their immediate vicinity (up to 60-80 feet away) from using cell phones.