About the projector has no signal，How to solve？

There is no signal on the projector, 1. may be incorrect operation 2., it may also be a signal line, for example, the quality of the signal line is too bad, too long, and the signal is weak. 3. may also be that the device that connects the projector is not set correctly, for example, the TV Box's video output resolution is too high, the laptop does not set the video output, and the DVD's output resolution is set too high. TV BOX, DVD can be set by remote control. The laptop can also be set up. 4., if there is no signal on every interface of the projector, it must be your operation is incorrect.