https://techcrunch.com/2021/07/27/rapidsos-ec1/

Numbers can take on profound cultural significance, but few numbers have quite the resonance as 911, the emergency number for the United States. Few want to dial it, but when they must, it works — every single time. One industry trade association estimates that 240 million 911 phone calls are made every year, ranging from the quotidian loud dog to the exceptional terrorist attack.

While it may be a singular number, 911 calls are directed to roughly 5,700 public safety answering points (PSAPs) across the country, all with independent operations, variegated equipment, disparate software, multifarious organizational structures, and vast inequalities of staffing and resources.