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https://www.perfectjammer.com/all-gsm-3g-jammers-blockers.html
GSM was the dominant 2G digital mobile phone standard for most of the world. It determines the way in which mobile phones communicate with the land-based network of towers. The mobile phone standard is implemented world-wide. There are a total of 14 GSM jammer fequency bands that contain both pre-set and dynamic channel allocations. The frequency ranges for each this frequency band are different, with frequencies ranging from 380.2 to 1990 Mhz. 921 Mhz to 1710.1 Mhz fequencies are not assigned to GSM bands and are assigned to other tasks by the FCC. Each this frequency band also makes use of a separate uplink and downlink frequency range within each pre-designated band. The uplink and downlink ranges are distinguished from each other in order to help minimize potential interference.