Advanced technology has brought convenience to mankind. Since the transmission power of the base station of mobile communication is very large, the closer to the base station, the worse the shielding effect. In foreign countries, mobile phone signal jammers are not new. In the past two years, it has been launched in the Chinese market, and some places in the classroom will install such WiFi interferers to prevent candidates from cheating. However, for more citizens, the abuse of such equipment may harm citizens' freedom of communication. http://www.jammer-buy.com/wifi-jammer/c-29.html