Wednesday, December 13, 2006

Cell phones for 911 emergencies

I briefly overheard on Fox News about how your cell phone can be used as a public safety tool. It's obviously to dial 911 even when the phone has no service or is out of range. But in recent news when James Kim and his family disappeared in Oregon, or when skiers go missing, cell phone technology comes into play.


Mobile devices, when they are within range, constantly let cell towers and the mobile switching center, which is connected to multiple towers, know of their location. The mobile switching center uses the location information to ensure that incoming calls and messages are routed to the tower nearest to the user.

If a subscriber is unable to get service, this location information is usually purged from the mobile switching center. But some location information may remain in call detail records. Some mobile operators may store the most recent communication between a device and a mobile switching center for a certain period of time, usually 24 hours.

When someone is missing, even this small bit of information can prove useful in determining the approximate location of a device using the updates from the mobile switching center. If the mobile subscriber is still within cell phone range, authorities can track his or her general movement by following the sequence of towers the phone has contacted or pinged. And if the cell phone goes out of range or runs out of battery power, the mobile operator may be able to use the last recorded location before the cell phone either lost its signal or lost power.

The bit of info I caught on the news is when you are hopelessly lost in a area unfamiliar, dial 911 when you can at the higest elevation. The signal can be triangulated between towers to pinpoint your location. Even if you're a bad dude on the run.

In fact, I understand from talking to Cingular One that a used cell phone without a sim card can call 911 without paying anything for service. Cell phones are regulated by the FCC. The FCC demands that ALL cell phones shall be able to dial 911. So next time when you're upgrading a phone, give that elderly next door neighbor your cell phone to stash in the car with the cigarette lighter charger. He/She doesn't have to have a telephone number or sign up for service... the cell phone can connect to 911.

photo source


Kate O' said...

"Even if you're a bad dude on the run."

Not that my brother is a bad dude -- he is a troubled dude with learning disabilities and behavior disorders -- but he once stole my mother's car and was gone for several days before police were able to locate him through records of car phone usage. And that was way back before the enhanced 911 stuff. So yeah, bad dudes using cell phones beware.

Kerry Woo said...

Kate O' - I've always seen in the movies where the po po track down the whereabouts of someone on the run using credit card transactions - that seems so low tech trying to catch up with someone now.