There is protocal for each type of call that comes in to a 911 center. Dispatchers are trained to asked certain specific questions (if possible) to obtain as much information as possible prior to sending responders into any given situation. In a situation such as 911 hang up call, the dispatcher will listen carefully to attempt to pick up any clues as to what is going on. Then they will attempt to recontact with the number that called. Usually at that point, units are dispatched to the location the call came from. The dispatcher may have the technical capability to replay the 911 call to see if they can pick up any additional clues upon listening to the call again. If the 911 center is not busy with other 911 calls, a good dispatcher will be doing background work for the officers. That nay include seeing who lives at that residence, finding out if there had been other calls for service there, seeing if there were guns registered, etc. This is based on my own experienced in 30 years of 911 public safety telecommunications; 15 years on the radio, and 15 years in management. I am now retired and although I wouldn't change a moment of my career, there are lifelong repercussions from things I will never un-hear.
