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Emergency Notification System

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Cass County 911
How 911 Works

With enhanced 911 the citizens telephone call is instantly routed to our communications center.

When a call goes out from your phone, your voice isn't the only thing being transmitted in the network. The phone company switch that serves your phone is also sending out an Automatic Number Identification (ANI) signal to the network.

Originally, ANI signaling was designed to assist the phone company in accessing toll charges for long distance calls. With advances in technology, it was eventually employed to aid in relaying needed information to the PSAP for 911 response.

How does it work? Within each call, information containing eight digits is embedded in the signal. These eight digits contain the seven digits of the caller's local number. The eighth digit is called a Numbering Plan Digit (NPD). NPD is basically shorthand for the area code of the originating call. Since most 911 tandems rarely dealt with more than two or three area codes, this was an economical way to relay information with one digit instead of three.

With special equipment, the 911 tandem can read the ANI information and route the callback number to a digital display at the appropriate PSAP. Armed with this ANI information, the PSAP has equipment allowing it to request and receive the caller's physical address or Automatic Location Information (ALI).

Below is a diagram of How 911 Works

A screen at the 911 center displays the telephone number as soon as the call is received. Within seconds the display will indicate the exact address the call is originating from. It will also display the proper fire, police and ambulance service for the address. Coin telephones will provide access to the 911 system free of charge.


If you accidentally dial 911 or hear the communicator answer:

"911 Do you need Police, Fire, or Ambulance?"

Please do not hang up.   All you need to do is explain you have dialed the wrong number. The communicator will confirm this with you by asking a few questions, to ensure you are safe and that there is no problem. If you do hang up without talking to a communicator, you will have company stopping in. It is this Sheriff's Office policy to send Deputies when a 911 caller hangs up.

Our 911 center is equipped with a Telecommunications Device for the Deaf (T.D.D./T.Y.Y.). This device will detect an in coming B.A.U.D.O.T or ASCII call and allow hearing impaired persons to report an emergency via a keyboard device directly to a 911 dispatcher.

The device is interfaced with the telephone system in our 911 center and will automatically alert the dispatcher of an incoming T.D.D./T.Y.Y. call. Our 911 communicators have been trained on the operation and use of the T.D.D./T.Y.Y. Hearing impaired customers will not have to call a translation service in an emergency; they too can dial 911.


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2501 West Mechanic Street, Suite 100, Harrisonville, MO 64701
Phone (816) 380-5200 - FAX (816) 380-8334
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