The entire frequency band of electromagnetic waves ranges from the smallest few Hz to the largest tens of hundreds of GHz. The range is very large. Each segment may be used as a communication signal. However, except for a small number of very professional equipment, ordinary mobile cell phone jammer All of them are “not loud enough” and “incomplete tones”. A mobile phone signal jammer can only block a small part of the frequency band, and communication tools can use the unshielded frequency band to communicate. Of course, all the 2G, 3G, and 4G mobile phone services of several domestic communication companies are concentrated in several small frequency bands, and the mobile phone signal jammers in the examination room can still concentrate on these frequency bands. When the mobile phone jammer is working, it will “sweep” electromagnetic waves from low frequency to high frequency in various frequency bands to interfere with the connection between the mobile phone and the base station.
The so-called shielding efficiency refers to whether there are blind spots or leaks in the shielding effect. In the vicinity of some prisons, there may be transmitting base stations with strong mobile phone signals. In order to achieve a good shielding effect, it will take a lot of materials and energy accordingly, and the cost will increase accordingly. Therefore, the better the shielding effect, the higher the cost will be. In practice, the shielding requirements of the prison area are generally higher, and there are slight leaks and blind spots. The offenders may seize this loophole, so that the mobile phone can be used in the originally stipulated shielding area, and the original intention of shielding the mobile phone cannot be achieved.