All mobile phone networks use radio signals that can be interrupted or even completely blocked

The main concept of jamming is the release of co-channel signals (noise) used by mobile service providers to suppress and disrupt user signals. The gsm jammer generates the desired frequency (noise) and then amplifies the generated frequency into the range of 800 MHZ to 1.4 GHZ to match the frequency of the cell phone sent by the base station.
When the phone displays "No Network", thus allowing no calls to pass through without interfering with other observed communication methods. More in-depth and in-depth research is needed to produce more complex and better jamming devices so as not to affect other base station transmission systems.