The GMDSS installation on ships include one (two on vessels over 500 GT) Search and Rescue Locating device(s) called Search and Rescue Radar Transponders (SART) which are used to locate survival craft or distressed vessels by creating a series of twelve dots on a rescuing ship's 3 cm radar display. The detection range between these devices and ships, dependent upon the height of the ship's radar mast and the height of the Search and Rescue Locating device, is normally about 15 km (8 nautical miles). Once detected by radar, the Search and Rescue Locating device will produce a visual and aural indication to the persons in distress.