Fecha de publicación: 11/02/2016 Fuente: WIPO "royal booby" A system for detecting underground tunnels. The system has a multitude of transparent receiving pipes that are positioned into ground at a given pipe spacing therebetween. A light sensor, connected to a control unit, is positioned at an upper end of each of the receiving pipes. When a receiving pipe is exposed to light from an underground tunnel, the light sensor senses the existence of light and passes a received signal to the control unit, which processes the received signal and activates a warning signal.