Where can mobile jammers be used?

Do you know the fact that certain places such as conference rooms, auditoriums, courts, libraries, examination rooms, schools, cinemas, theaters, hospitals and mobile phones are not allowed? Even if you are very personal, you can completely avoid making big phone calls and texting. Noise is annoying, and cell phone signals may cause interference. Then do you know why you can't use mobile phones in these places? Because they are generally equipped with high-power mobile cell phone jammer, fortunately, today you can easily buy a good mobile phone jammer to prevent this. The app of the jammer kit cannot run normally because there is no service on the phone screen.