* = Changes are planned: Within (unknown time frame), 911 calls from cellular and "personal communications system" phones will go to local agencies, based upon the location of the cellular site ("tower") closest to the user. Because radio waves do not respect political jurisdiction boundaries, some of those calls will go to the wrong agencies. Therefore, it will still be necessary for callers to have a good idea of where they are and which agency they need.
It is not always possible for every citizen to dial 911 and have their particular emergency call go to the correct police or fire dispatch center immediately. Every agency will do as much as they can to get your call to the correct dispatch center; but every caller can contribute to the speedy handling of calls by knowing (a) where the emergency is, and/or (b) what agency they need. Yelling at the dispatcher "Just get someone out here," is counter-productive and will not help.
Beginning a conversation with "I am reporting a (type of emergency) at (location)" can put you well on the way to getting help to the scene much more quickly.
For additional tips regarding proper reporting of emergency situations, see How To Be A Good R.P.