GSM signal is a type of cell phone signal, so
GSM jammer belongs to mobile phone jammer. If you just want to block GSM signal, you only need to choose only can interfere with the GSM signal of the device, but if you in addition to the GSM signal, also want to block other cell phone signals, such as 3 g, 4 g signals, then I suggest you buy a GSM 3 g 4 g cell phone jammers.