A reverse phone dir or directory is a fantastic collection of names, addresses, and telephone numbers that can be used to locate a person or business, just by using a phone number. The phone number in question is entered, ran through a database that is filled with numbers, names and sometimes addresses, then the information is produced for the seeker. This is a quick and easy way to determine who a phone number belongs to. There are many free services for this on the internet, but mostly for land lines.

These directories aren't only for the general public, these are even used by law enforcement and many other emergency services. It is a great way to determine the caller during instances when someone calls and then quickly hangs up or becomes disconnected in some way.

If someone calls 911 and then is unable to give directions to the location where he/she is at, the dispatchers are able to perform a reverse phone look up using the directory connected with their phone system.

Once the number is matched with a name and address, the dispatcher can then tell the ambulance, police, or fire department where the location of the emergency is. This feature has saved many lives.

The main difference between the directory that the public has access to and the one the emergency services use is that the public directory doesn't contain all numbers for landlines. It won't have any unlisted numbers in it and not all land line telephone numbers will be current.

There also won't be any cell phone numbers listed in the public directory. Cell phone numbers don't come in the phone book that is printed and sent to everyone, so they aren't public knowledge. There are some databases that pay cell phone services to obtain a list of their customers and their information, which they will then sell to the public for a fee as well. This private directory can be automatically accessed by emergency services, for safety purposes, but the general public must pay per search.

The option to pay a yearly fee is offered by some services, but most people just pay per number they look up. Reasons why someone might want to look up a cell phone number, instead of simply hitting redial and seeing who answers, is in the case of harassing phone calls. There are times when people accidentally dial a wrong number, most will say they are sorry and hang up. Other instances involve people who are intentionally dialing random numbers, just to see who answers at the other end.

These random dialers don't often call the same person twice. The people who do end up calling the same number over and over again often have an agenda. They are either trying to be annoying or they are having a vendetta with someone. In either case, the person being harassed can go to the police and provide them with the phone number of the harasser, or they can use a reverse phone dir to find out who it is.