If you are a heavy mobile phone user, then the battery and signal of the mobile phone is the lifeline, the battery is below 50% or the signal is not satisfied with the feeling of feeling uncomfortable and insecure. For such heavy cellphone dependence, the most unpleasant days of the year are the three days of the college entrance examination
The college entrance examination is a fixed program in June every year. During the three days of the college entrance examination, apart from the continuous news reports and the unprovoked crowding in the schools passing by, the most impressive thing is the poor cellphone signal caused by the cell phone jammer in running during the examination.
The signal mask was not originally designed for the test scenario. The signal shield was originally used in prisons.
In order to ensure the information security and privacy of the high-walled compound of the prison, it is necessary for the prison to isolate the communication signals from the prison, which is the original intention of the signal shield.
When the signal shield was first invented, the world was only in the 2G era. At that time, there were three operators in China, but in fact, all the mobile phones used second-generation network communication technology. The frequency of communication between different manufacturers varies greatly.