People with speech disabilities who have trouble talking on the telephone, may just be silent when calling 9-1-1.
About 25% of 911 calls tend to be "silent" calls. For example, should there be a fire, one would just dial 911 and leave the room. One with a heart attack wouldn’t be able to talk on the phone after dialing 911. One may dial 911 without talking should there be an intruder in the house. All 911 dispatchers are trained to listen to the sounds of the call which service would be dispatched. Crackling sounds may indicate that fire engines are required. Screaming or threatening voices may indicate police are needed. Gasping for air may indicate ambulances are needed.