Less complex gsm signal blocker devices can block a frequency group, while complex GSM jammer can block multiple types of networks simultaneously to disable dual-mode or triple-mode phones, which can automatically switch between different types of networks To find the open signal. Some high-end devices block all frequencies at once, while others can tune to specific frequencies.
To disrupt phone reception, all you need is a device that broadcasts at the correct frequency. Although different cellular systems process signals differently, all cellular networks use radio signals that can be interrupted. GSM for digital cellular and PCS systems operates in the 900 MHz and 1800 MHz bands in Europe and Asia and the 1900 MHz band (sometimes referred to as 1.9 GHz) in the United States. The high-power GSM jammer can broadcast on any frequency and is effective for AMPS, CDMA, TDMA, GSM, PCS, DCS, iDEN and Nextel systems.
The actual shielding range of a jammer depends on its power and local environment, which may include hills or walls of buildings that block interference signals. Low-power jammers block calls within approximately 9 m (30 feet). More powerful troops have created a unit-free area as large as a football field. The equipment used by law enforcement can be taken out of service 1 mile (1.6 km) away.
During hostage incidents, police can control time and location sensors to switch phones. Police can ban phone calls during the anti-drug operation so that suspects cannot communicate outside the restricted area. GSM signal jammers can be used in areas where radio transmission is dangerous (potentially explosive gases), such as in chemical storage facilities or grain elevator areas.
