There are large and small wifi jammer. There are many channels in any frequency band of mobile communication. In professional terms, it is a channel, and a channel can be used as BCH. : BCH, which can be determined by the MSC according to the channel distribution in the entire network area, but anyone who understands knows that BCH is not fixed, the shielding situation is uncertain, and even some cells will be placed. Two or more BCH, so when using a wifi signal jammer, it is to interfere with all channels within the range of use that may appear in the mobile communication network, which is commonly referred to as CDMA, GSM, DCS, PHS, TD- SCDMA, WCDMA, etc., the frequency interference in these channels is used to interfere with our mobile phone signal, which cuts off the channel for the mobile phone to receive signals as a whole.