Radar Detector RD-400 To Help Locate Survivors Buried Under Rubble and Debris. The RD-400 is portable radio detection system designed to locate survivors buried under rubble or debris by either movement or breathing. The RD-400 is based on GPR technology, which allows it to accurately pinpoint the location of a survivor and determine the distance to him or her. It is utilized for emergency teams during search and rescue operations after a catastroc attack or a natural disaster. The device is very simple to operate. It turns on with a single press of a button, sending GPR wreckage, quickly fixing on any movement or breathing. An accompanying Tablet PC displays the distance to the survivor using a red movement and a blue breathing.