The working principle of mobile communication is to connect with surrounding base stations during communication, then access the core network, and finally find the communication destination. In the whole process, all information is undertaken and transmitted through electromagnetic waves. The electromagnetic wave frequency band used by mobile phones is related to the system used by the mobile phone and the operator. However, the electromagnetic wave frequency band used by the three operators is distributed in the range of 850-4900MHz. If you want to shield the mobile phone signals in the exam room during the exam, it is impossible to make the 2G/3G/4G/5G base stations around the exam room not work, otherwise all the communication equipment in this area will not be able to communicate normally. Therefore, only mobile phone signals in the examination room can be shielded.
When it comes to shielding mobile phone signals, the first thing you think of is metal shielding. Put your mobile phone in a closed metal box, and pass through the metal to block the propagation of electromagnetic waves. However, it is obviously impractical to design all examination rooms as metal-enclosed classrooms. How to block the signal in the examination room? In fact, it can be achieved by applying a small cell phone signal jammer.
The working principle of the cell phone jammer is to scan from the low frequency band of the forward channel to the high frequency band at a certain speed, so that the mobile phone interferes in the process of receiving the message signal, so that the mobile phone cannot detect the normal data sent from the base station. A connection is established with the base station, and there is a state of no signal and no service.
Nowadays, the mobile phone signal jammers used in examination rooms are all full frequency bands. It can interfere with all the frequency bands of the three operators 2G/3G/4G/5G, and WIFI signals and Bluetooth signals can also be completely shielded. The above is the principle of mobile phone signal jammer. However, the frequency range of electromagnetic waves ranges from a few Hz to hundreds of GHz, and each segment may be used as a communication signal. So are there some special frequency bands used in the examination room? This is true for other radio communication tools, so radio communication tools with dedicated frequency bands have emerged in this context. The working frequency band of the device is selected outside the frequency range covered by the mobile phone jammer, so the mobile phone signal jammer cannot shield them. But rest assured, for this kind of special radio communication tools, the examination room will be specially equipped with a monitoring vehicle with a radio monitor to monitor it in real time and cut off the radio wave signals from unknown sources.