As the popularity of mobile phone, it is frequently discovered that many students cheat in exams by using a mobile phone. In case of cheating, most of the exam rooms will fix a mobile phone signal jammer to block mobile phone signal. However, due to inappropriate use of the jammer, people near the exam rooms also have troubles to use their cell phone for communication.

         Though the signal jar is full, cell phone is unable to call someone or receive calls. Sometimes people get through to somebody successfully, but the signal is off and on. Residents around the high schools complain that they cannot use cell phone for communication every time high schools organize large exams. The mobile phone jammer influences the life of near residents terribly. It is dangerous for residents to block their cell phone signal if there is an emergency. Faced with these critics, teachers of the high schools are helpless, because the jammers are sent to the school uniformly and they don’t know how to adjust them.