Astro is the premier high-sensitivity GPS-enabled tracking system for sporting dogs. This unique system pinpoints your dog's position and shows you exactly where he is, even when you can't see or hear him. The Astro 320 handheld GPS device has features that hunters have been asking for - like increased range, a simplified user interface and must-have mapping capability. The Astro system includes the redesigned Astro 320 and the rugged, orange polyurethane DC 40 transmitter collar. The collar accommodates most e-collar receivers, eliminating the need to put two separate collars on a dog. Plus, collar lock creates a 4-digit PIN number that helps prevent others from seeing your dog's whereabouts - a useful feature in field trials to ensure that an Astro is used only as a recovery tool when a dog in competition becomes lost.