Under a federal mandate known as E911, they had to upgrade their networks to ensure that anyone dialling the 911 emergency number could be located to within 100 metres.

• 遵照一条叫做E911的联邦法令，他们要升级服务网络，确保能找到任何拨打911呼救电话的人所处的位置，误差不超过100米。