What happens if 911 gets a call and there's nobody talking?: originally appeared on Quora: The best answer to any question. Ask a question, get a great answer. Learn from experts and access insider knowledge. You can follow Quora on Twitter, Facebook, and Google+.
First, the call-taker listens to the line to determine if they can hear anything that might indicate the reason for the call (such as sounds of a struggle, screaming, children playing, gunshots, etc). This information will help the call-taker determine the nature of the emergency and whether to dispatch police/fire/EMS. The call-taker will ask the caller to make a noise or tap the phone to confirm the caller needs help. Sometimes the call might be an erroneous "butt dial" or it could be someone under duress or suffering a medical emergency that impairs speech (such as a stroke).
If the caller is using a landline, call-takers in a public safety answering point (PSAP) can usually trace the call automatically with location data provided by the telephone service provider. However, the FCC states that 70% of 911 calls are placed using a cell phone. It's a little bit more difficult to identify locations with cell phones (especially if the caller is in a multi-story structure). FCC Phase II E911 rules require wireless service providers to provide more precise location information to PSAPs; specifically, the latitude and longitude of the caller. This information must be accurate to within 50 to 300 meters depending upon the type of location technology used. Notice how the Phase II rules don't include altitude? It's very difficult to ascertain which floor a caller is on when using a cell phone.
Call-takers can also look up or contact wireless companies to get subscriber information (such as the address used to register for the account) to give more clues as to the caller's location. However, if your wireless phone is not "initialized" (meaning you do not have a contract for service with a wireless service provider), and your emergency call gets disconnected, you must call the emergency operator back because the operator does not have your telephone number and cannot contact you.