Precautions: 1.The jammers are customized according to the frequency bands of different countries, please confirm that the purchase country and the actual use country are consistent. Otherwise it can not be used.Please read the jammer function before purchasing. 2.If the low power jammers(such as handheld jammers) to blocker signal device(such asWIFI router, Bluetooth audio equipment, etc.), the effect will be poor or even can not jammer. 3.It is forbidden to use while charging. 4.Do not use handheld jammers as desktop jammers. 5.Do not use jammers before connecting the antenna.