The signal jammer of the mobile phone scans during the working process at a certain speed from the low frequency band (the channel from the base station to the mobile phone) to the high frequency band and forms interference when the mobile phone receives the message signal that the mobile phone cannot recognize the normal transmission of the base station data and thus none Can connect to the base station and has no signal or service status.
When we use a cell phone, under normal circumstances, the cell phone is first connected to the carrier's base station and the radio wave signals sent by the two parties come and go. When the jammer is switched on, however, it "strikes the gongs and drums" around the mobile phone and emits "noise" radio signals that are many times greater than the signal power received by the base station., The connection between the two has been severed. Whether you are making calls, texting, or performing other functions, everyone is in a paralyzed state.
In fact, this is not done to shield the cellphone signal, but to cancel the signal sent by the cellphone in a large number of noise signals to achieve the purpose of interference.
Currently, the cellphone signal jammers used in the exam room are all full frequency bands that can interfere with all frequency bands of the three operating 2G / 3G / 4G / 5G, and WIFI signals and Bluetooth signals can also be shielded.
The above is the principle of the cell phone signal jammer. However, the frequency range of electromagnetic waves is from several Hz to several hundred GHz, and each segment can be used as a communication signal. Will there be special frequency bands that will be used in the exam room?