That's my understanding. It's rather necessary here in AZ where "cells" can be miles apart, due to the low density.
Like Maricopa County is larger than Massachusetts. And a suburb, Chandler, is larger than ALL of New York City ;-) And the state is about the same size as unified Germany.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
Why does the 911 call center have to have any specialized equipment? AIUI all the hardware is in the cells. 911 asks the cell for the location of the call (I'm told the location finding equipment doesn't even have to be GPS).
Again, why does the 911 call center need the capability? The call is coming through the cell. Land lines come through the LATA. Both have to supply the location of the caller.
-- Keith
Thanks for the explanation.
First off, a 911 center always had specialized equipment. Unlike a regular telephone switchboard, a 911 center had the ability to seize the trunk if the caller hung up, and some other features as well. This was the thing that set 911 from a plain listed number, "911" was more than a dialing convenience, it was a system specifically set up to route and control emergency calls.
Later generations of 911 provided the address of the caller based on a database. This was not so easy to develop because telephone company exchange boundaries did not necessarily coincide with public safety boundaries. (Where I live there is no correlation between municipal, postal, common name, and telephone exchange boundaries at all.) Obviously the 911 center had to have a display linked to the phone line to display the information along with the call.
If I understand what you're saying: that for a cell phone call, the cellular system, not the 911 center, reads the data sent from someone's cell phone (or does a triangularation) and sends that data to the 911 center in the same format as a landline address. With that, little modification of the 911 center would be necessary--the center of course would need to know the caller is from a cell phone and the location provided is rough, as a opposed to a given street address (which might include an apartment number, something obviously GPS couldn't do).
Of course, all cell towers must be so modified to do either triangulation or receive the cell phone's GPS data and then pass it along accordingly. But that seems to be mostly a software modification. (Triangulation would be hardware, though).
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