http://www.insidebayarea.com/localnews/ci_3702339 Heather MacDonald"ShotSpotter's technology analyzes the sound, up to 1.5 miles away, and uses three different sensors _ no bigger than a toaster and usually mounted on flat top roofs connected to telephone lines _ to triangulate the location of the gunshots, typically within 10 to 30 feet, according to James G. Beldock, president of the Santa Clara-based company. The microphones can distinguish between shots and other similar sounds, including fireworks and car backfires, Beldock said. The system also has proven effective in deterring random gunfire and celebratory gunfire, common in many Oakland neighborhoods on holidays, he added.
Too often, by the time the reports of shots fired are logged and officers are dispatched, the shooters are long gone. In addition, callers are unable to tell police the specific location of the gunfire."
