The cell phone must be able to be used normally, unless the cell phone signal in the place where it is used is very strong, that is, there is a signal amplifier nearby or in a building. For example, if a mobile signal amplifier is installed in the building, it is difficult to cut off the mobile phone. If it is a connected signal amplifier, it is difficult to cut off the connected mobile phone. Therefore, the only way to make a mobile phone usable is to install a mobile phone signal amplifier where it is used.

The working principle of the mobile phone: In a certain frequency range, the mobile phone and the base station are connected by electric waves, and the data and sound transmission is completed with a certain baud rate and modulation method. The working principle of the signal jammer: the jammer must scan to the low end frequency of the channel at a certain speed as soon as possible during the work. This scanning speed causes garbled interference to the message signal received by the mobile phone, and the mobile phone cannot detect normal data sent by the base station, and cannot establish a connection between the mobile phone and the base station. Mobile phones are manifested by phenomena such as network search, no signal, and no service system.