There is no mobile phone signal around the school
Every year during the high school and college entrance examination, there will be network problems around the school, such as dropped phone calls and slow Internet access. This is because the school has turned on mobile phone jammers. If we regard the mobile phone as a handheld two-way radio, the radio can be interfered, and the mobile phone is no exception. Just like any radio, the signal of a mobile phone can be disturbed.
The principle of the mobile phone signal jammer is: within a certain frequency range, the mobile phone and the base station are connected by radio waves, and the data and sound transmission is completed with a certain baud rate and modulation method. In view of the above communication principle, the portable jammer scans from the low end frequency of the forward channel to the high end at a certain speed during the working process.
This scanning speed can constitute garbled interference in the message signal received by the mobile phone, and the mobile phone cannot detect the normal data sent from the base station, so that the mobile phone cannot establish a connection with the base station. The mobile phone is manifested as a search network, no signal, and invalid labor system. Eventually, the mobile phone has no signal and cannot receive text messages or calls.
Wireless communication is the use of electromagnetic waves to stop communication. The functional characteristics of electromagnetic waves are determined by its frequency. Our mobile phone must emit electromagnetic waves that meet the request to connect to our communication carrier base station. The fundamental principle of the mobile phone's interference device is to transmit the same radio frequency as the mobile phone. Because of the same frequency, the mobile phone can't tell which signal is the base station signal on the track, thus completing the "interference". So how is this kind of multi-network interference accomplished? it's actually really easy. It is to repeatedly play the interference bands corresponding to the three signals in a loop, and cover the three bands at once, and the distance of this loop is so small that the mobile phone can only sit down when there is basically no speech.
The main principles of signal shielding and signal jammers are currently in the frequency band used by mobile phones, which emit loud noises, disturbing the reception and transmission of normal signals of mobile phones. This small object is not only used to avoid cheating during exams, it is also often used politically and militaryly to avoid fear attacks.