What is the principle of the wifi jammer used in the college entrance examination? Does it really work?

To put it simply, a wifi jammer is a jammer that makes radios, mobile phones, Bluetooth, and WiFi signal frequency bands within a certain distance noise, so electronic devices such as mobile phones and radios lose their communication signals. It's like you are in a noisy market, others can't hear what you say, and you can't hear what others say. Hearing and speaking are useless. The wifi signal jammers used in schools and examination rooms generally have an effective distance of 200 meters. And generally, many sets will be installed, repeated coverage, and enhanced shielding. If you want to hold up a larger "shielding umbrella", you need more professional equipment, usually, a signal shielding car will come over. Be careful: the original wifi frequency jammer was designed to fight crime and serve law enforcement agencies and the military. In fact, buying a signal jammer by yourself would be suspected of breaking the law, and the wireless signal jammer falling into the hands of criminals may cause serious damage as a result.