COMMUNITY ADVISORY
Where Does Your Cell Phone 911 Call Go?
Over 30,000,000 emergency calls are placed every year from
cellular phones.
A cellular phone is a powerful tool for reporting emergencies,
but you need to know how your cell phone works when you dial
911. This Community Advisory has been written because of a recent
incident near the Maryland/District of Columbia border where
the wrong 911 center was reached from a cell phone. We hope
you can take a minute to familiarize yourself with this important
issue.
How does cell phone service work?
A cell phone system divides a region into smaller areas called
cells. Each of these cells has a site with its own low powered
radio transmitter/receivers and antennas. These cell sites are
connected to a main telephone switching office (MTSO) that in
turn is connected to the local public telephone network. When
a call is placed on a cell phone, the transmission is automatically
sent to the nearest cell site. The site transmits the signal
to the MTSO where upon it is connected to a landline telephone
network or a cell phone network, depending on the party called.
This system can cause 911 routing problems if the receiving
cell and the MTSO are not in the same jurisdiction as the emergency.
This has occurred when 911 calls are placed near the Western
Avenue corridor. The 911 caller may be significantly inside
Maryland, but if the phone's signal is received by a cellular
site in the District then the 911 call will automatically be
routed to the District of Columbia's 911 Communications Center.
By 2001, the Enhanced 911, or "E911," mandate requires
cellular phone manufacturers to incorporate the technology that
will pinpoint the caller's location within 400 feet. That system
is not currently in place in our area, so the Rescue Squad wants
to remind the community to be aware of potential problems that
may occur when using a cell phone to call 911 and what to do
to ensure emergency help is on the way.
- Never hesitate to dial 911 to report an emergency!
- Always tell the 911-call taker what jurisdiction you are
in and ask the 911-call taker what agency they are with. Never
assume that you are talking to the correct communications
center.
- Try to have a by-stander also use a regular hard-line telephone
to report the emergency, if possible.
In summary, cellular phones are valuable tools in an emergency.
However, a few precautions by the cellular phone user will assist
public safety personnel in reaching your location quickly. For
further information, please contact Chief Edward Sherburne of
the Bethesda-Chevy Chase Rescue Squad at (301) 652-0077.
Contact: Peter H. Morris, Assistant Chief
(301) 652-0077 x204
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