Why is there no signal in the elevator?

The reason why there is no signal in the elevator may be that the steel structure inside the elevator will interfere with the signal, resulting in the failure of mobile phones and other equipment to connect to the network normally. In addition, elevators usually have thick metal doors, which will form a shielding effect, resulting in the signal can not pass. However, some high-end elevators adopt special technology to solve this problem and provide mobile communication services inside the elevator.