Mobile phones can be used not only for communication, but for tracking the movements of their owners as well. Law enforcement officials in the US have been using the signals emanating from the handset to secretly monitor the movements of suspects as they occur, after easily obtaining court orders. Cellular operators like Verizon and Cingular are able to determine their subscribers location, within about 300 yards whenever a phone is turned on. The operators turn over location information when presented with a court order to do so. Requests for issuing court orders, however, have come under tougher legal scrutiny in the past few months after three federal judges have denied prosecutors the right to get cellphone tracking information from wireless companies without first showing "probable cause" to believe that a crime has been or is being committed (standard applied to requests for search warrants). Their argument to do so was the fact that surveillance by cellphone acts like an electronic tracking device that can follow people into homes and other personal spaces, therefore they must meet the same high legal standard required to obtain a search warrant to enter private places. These judges' rulings are provoked by the growing debate over privacy rights. They do not bind other courts, but could significantly prolong the access to cell location data if other jurisdictions adopt the same reasoning.