Normally I wouldn't post such a document to this intelligent community, but it never fails to surprise me how many people call in with stupid questions. Any chance to educate the people I help, or anyone else helps, is great. So here goes.
Who am I calling?
All calls to 9-1-1 are directed to a Primary Answering Point (PAP). In my city, it's the police department. All calls which the local phone company determine are coming from within the city jurisdiction come to us. We have one computer at each station (we call it the VESTA, but it's just the name for the software it runs) that displays all of our 911 lines, emergency lines, administrative lines, non-emergency lines, and then our direct dial lines, which are dedicated phone lines or radio links to the county sheriff, fire dispatch, and our tow service. When we receive a 911 call, we immediately see the number through Automatic Number Identifier (ANI) which is then automatically run through our Automatic Line Identifier (ALI) to get full account information. If the call is in our jurisdiction, we make up a call for service. If it is a fire/medical call, in the sheriff jurisdiction, or in the highway patrol jurisdiction, we can immediately transfer it accordingly.
What do you know about me?
As soon as you call, we know your number through ANI. This is regardless of whether or not you have Caller ID Blocking, or hang up before we pick up. This is automatically routed to our ALI system which then produces even more information. From that we get your telephone number, your street address (as it is listed on your phone bill), your name, what kind of line you are calling from (PBX lines, where you have to dial "9" before getting a dial tone, etc), whether you are calling from a business, residence, or payphone, and the billing number (often times, especially with PBX lines or businesses, a place will have multiple lines all put on one bill. It lists the master number for us), and then the appropriate Police, Fire and Ambulance agencies to handle the jurisdiction. Remember all lines are recorded, and all lines can be subpoenaed for court at any time.
When should I call, and when should I not call?
The simplest answer is, whenever you have an emergency. One thing I hear most often when I ask "What is your emergency?" is "I don't have an emergency." Yes we can transfer you over to our non-emergency lines, but that can take anywhere from 10-15 seconds, in which time any other person waiting to be answered could die. More specific, call to report a crime in progress, any medical emergency, any fire, any life threatening situation, or any other situation that requires IMMEDIATE assistance. Never call back to 9-1-1 to cancel a call, never call back on 9-1-1 to ask when police will arrive, never call back to do anything but state that a life threatening condition, or any other emergency condition exists that did not exist when you originally called or you did not state in your original call. Police departments ALWAYS have non-emergency numbers... they are always in the phone book. If your call is important enough to call the police for, it is important enough for you to look up a phone number.
What should I do when I call?
First and foremost, stay calm. Panic is your worst enemy in any situation. Next, don't tell stories. The officers that respond can hear what happened three years ago, but we need to know what is going on now, so we can dispatch officers now. Don't try and guess what we are going to ask. We know your address, and we are asking you questions in a way that will allow us to enter it in quickly so that we can get you help fast. Focus on what the operator is telling you, not on what is going on around you. We understand that you are in a stressful situation, but we need to know what is going on. Also understand that just because we have you on the phone doesn't mean help is not on the way... I can dispatch officers before you say a single word, and I don't have to be off the phone to do it. Don't make things up and don't guess. Letting us know that you don't know something is just as important as answering a question. Any misstatement could put you in a potentially life-threatening situation.
Other pointers
If you have a cell phone, program in your local police agency's seven digit emergency number. This should be in the phone book in the government listings. It will say something like "emergency 911 or 555-5555". If you can't find it (and you've actually looked) call your local agency's non-emergency number and ask for it. The reason for this is when you dial 9-1-1 from a cell phone, it is (currently) routed to a statewide dispatch center. This can add to additional delays. Of course, if you are on the freeway, or are out of your city, always make sure you dial 9-1-1, as this will be the fastest way to get assistance. Also, don't get mad at the operator because an officer is not there yet or you are having a bad day. All they can do is take your call. It is not their fault. Try not to get too worked up that an officer hasn't shown up yet. For many calls, such as house burglaries, and other calls with no suspects, remember that a few minutes of delay is going to make no difference in whether or not the crime is solved. Also remember that no matter how important this seems to you, there are many emergencies that require more immediate response. Remember that for every minute someone is not there taking your report, that is one more minute they are helping another person.
And finally
Don't dial 9-1-1 and hang up. It wastes time and resources, and can delay assistance to people having life threatening emergencies. If you misdialed, stay on the line and tell the operator. You're not in trouble. Everybody makes mistakes. Own up to yours.
Bottom Line... common sense, folks.