How it works in mobile communication
To know what the shielding signal does, let's first understand how mobile communication works.
As a mobile communication device, a mobile phone needs to establish a connection with a nearby base station first, and then access the core network to find a communication destination.
In the above process, all information is carried and transmitted by electromagnetic waves. The electromagnetic wave frequency band used by the mobile phone is related to the standard and operator of the mobile phone. But in general, the electromagnetic wave frequency bands used by the three operators are distributed in the 850-4900MHz range. If the organizer of the college entrance examination wants to block the mobile phone signals in the examination room, it is impossible for the 2G/3G/4G/5G base stations near the examination room to not work, otherwise all the communication equipment in this area will not be able to communicate normally. That's the only way to block cell phone signals in the exam room.
When it comes to shielding mobile phone signals, the first thing that comes to mind must be metal shielding, that is, placing the mobile phone in a closed metal box to block the propagation of electromagnetic waves through metal. However, it is obviously not practical to make all the classrooms in the examination room into metal-enclosed classrooms.
What should we do?
It's very simple, just need a small signal blocker to block all mobile phone signals in the test room.The principle of blocking mobile phone signals
The mobile phone signal jammer scans from the low frequency band of the forward channel (the channel from the base station to the mobile phone) to the high frequency band at a certain speed during the working process, causing interference in the process of receiving the message signal by the mobile phone, so that the mobile phone cannot detect the signal from the base station. The normal data sent out, so that the connection with the base station cannot be established, and there is no signal and no service state.
For example, when the mobile phone communicates with the base station, the signal jammer is like a troublemaker, deliberately making noise around you. The noise signal is so large that the mobile phone can't hear what the base station is saying, and the base station can't hear what the mobile phone says. In fact, this is not to shield the mobile phone signal, but to bury the signal sent by the mobile phone in a large number of noise signals, so as to achieve the purpose of interference.
At present, the signal jammers used in the examination room are all frequency bands, which can interfere with all frequency bands of 2G/3G/4G/5G of the three operators, and can also block all WIFI signals and Bluetooth signals.
The above is the principle of mobile phone signal jammer. However, the frequency range of electromagnetic waves is from a few Hz to tens of hundreds of GHz, and each segment may be used as a signal for communication. Will there be some special frequency bands used in the examination room?
Other radio communication tools
Indeed, radio communication tools in dedicated frequency bands are "emerging" in this context. The working frequency band of these devices is selected outside the frequency range covered by the cell phone jammer, and the cell phone jammer does not work on them.
For this special radio communication tool, the examination room is specially equipped with a wireless wifi signal jammer for real-time interference with radio wave signals of unknown origin.
Nowadays, drones have also appeared in the college entrance examination room, which can perform signal positioning faster.
Therefore, neither mobile phones nor these special radio equipment can play a role in the college entrance examination room.
Just as communication engineers are guarding the world's communication network all the time, at such an important moment as the college entrance examination, there are also many college entrance examination workers guarding the candidates and building a fair test environment.
