When the cell phone jammer is turned on, it can block all 2G, 3G, 4G signals, 2.4g WIFI signals and bluetooth signals from the three operators of China mobile, China unicom and China telecom. The principle of jammer is to jam the frequency sent by the receiving base station and wireless router, so as to block them. After the cell phone is blocked, it does not necessarily show no service. It may have one or two bars of signal, but it is virtual, and it cannot make phone calls or surf the Internet. To be specific, the closer to the shield phone will basically show no service, far from the shield phone will have a signal grid, the farther away from the more signal grid, until the phone can communicate to the Internet.
The mobile phone signal jammer can scan from the low frequency of the front channel to the high frequency at a certain speed in the process of working. The scanning speed can form scrambled codes in the received message signal of the mobile phone
In the process of working, the phone shield scans from the low frequency of the front channel to the high frequency at a certain speed. The scanning speed can form chaotic code interference in the signal received by the mobile phone. The mobile phone cannot detect the normal data sent from the base station, so the mobile phone cannot establish a connection with the base station. Mobile phone performance for search network, mobile phone no signal, no service system and other phenomena. Some venues deliberately did not block operators’ 2G spectrum, which allows voice, text and Internet access, for special needs. However, now operators are vigorously developing 3G and 4G networks, and 2G networks are only responsible for voice and SMS. For example, China mobile, when conducting voice calls, it will jump back to 2G band for communication without the function of VOL call. Now, it is very slow to use 2G network.