That creates a different problem, which is also dangerous. In a large company, you want physical security to know when there's an emergency. They can usually g

That creates a different problem, which is also dangerous. In a large company, you want physical security to know when there's an emergency. They can usually get to the scene much, much quicker, and will need to let emergency services into the building anyway. With landline corporate phones, they can be configured so that if the user direct dials 911, they can flag the extension and flash an alarm in the security office. Hotels often have a similar setup. (Avaya calls it "On-Site Notification", Cisco calls it "Cisco Emergency Responder".) If employees/guests are direct dialing 911 from a cell phone, building security has no idea what's going on.