When the mobile phone communicates with the base station, the mobile cell phone signal jammer is like a troublemaker, deliberately making noise around you. The noise signal is so large that the mobile phone can’t understand what the base station is saying, and the base station can’t hear what the mobile phone is saying.
In fact, this is not to shield the mobile phone signal, but to obliterate 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 mobile phone signal jammers used in the examination room are all full frequency bands, which can interfere with all the frequency bands of the three operators 2G/3G/4G/5G, and WIFI signals and Bluetooth signals can also be shielded. The above is the principle of mobile phone jammer. However, the frequency band of electromagnetic waves ranges from a few Hz to several hundreds of GHz, and each segment may be used as a communication signal. Will there be some special frequency bands used in the examination room?
As a mobile communication device, a mobile phone needs to establish a connection with a nearby base station when communicating, and then access the core network to find the communication destination.
Indeed, radio communication tools with dedicated frequency bands “came into being” in this context. The operating frequency band of these devices is selected outside the frequency range covered by the mobile phone jammer, and the mobile phone jammer does not work on them. For this special radio communication tool, the examination room is specially equipped with a monitoring vehicle equipped with a radio monitor for real-time monitoring of radio wave signals from unknown sources. So how exactly does the radio detector work? Because electromagnetic waves have the characteristics of “near big and far small”, by constantly moving the detection vehicle, the monitoring equipment can locate the signal transmitter according to the distance and the strength of the signal, and capture the offenders who use these radio communication tools on the spot. Nowadays, drones have also appeared in the examination room, which can perform signal positioning faster. Therefore, neither mobile phones nor these special radio equipment can play a role in the examination room.