911 (emergency telephone number)
911, sometimes written 9-1-1, is an emergency telephone number in Canada and the United States, one of eight N11 codes of the North American Numbering Plan (NANP). Dialing 911 from any telephone will link the caller to an emergency dispatch office—called a public safety answering point (PSAP) by the telecommunications industry—which can send emergency responders to the caller's location in an emergency.
Source: Wikipedia — 911 (emergency telephone number) (CC BY-SA 4.0)