For example, the multipath phenomenon, in which buildings and walls bounce multiple copies of a signal to a receiver, was once just the source of ghosts in television pictures.

• 就以多路径现象为例，讯号在传递至接收器的过程中，若碰到建筑物和墙壁，会反射出多个重复讯号，之前人们认为它只是电视画面上鬼影的罪魁祸首。