Path: utzoo!telecom-request
Date: Fri, 17 May 91 15:01:31 CDT
From: u1906ad@unx.ucc.okstate.edu
Newsgroups: comp.dcom.telecom
Subject: Re: Cellular Phone Use in Aircraft
Message-ID: <telecom11.368.6@eecs.nwu.edu>
Organization: TELECOM Digest
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X-Telecom-Digest: Volume 11, Issue 368, Message 6 of 7
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Recently somebody was wondering about the warning signs seen around
areas where explosives are being used, advising people to turn off
their cellular phones and two-way radios.  While I am not an
explosives expert, I can comment on the reason for this prohibition.

     Some of you have probably had the unpleasant experience of
hearing a CB or other type of radio transmission over something that
wasn't supposed to be a radio such as a stereo amplifier or telephone.
This happens because the radio frequency signal is changed from
alternating current to direct current by solid-state components in the
system getting the interference.  The DC signal is an extra voltage
introduced randomly into the system which can have unpredictable
results.  

In an amplifier, it causes noise or actual audio to be heard.  In a
computer system, it may scramble data and cause a system crash.  While
the detonators used on a construction site, for example, may not be
radio controlled, the wire leading to them can act as an antenna.  A
nearby radio transmitter might just develop enough current in the wire
to trigger the detonator.  

Finally, mobile phones and frequency-trunked radios should probably be
turned clear off because they can automatically transmit as a result
of a command from the controlling system such as the answer to a ping.
When considering the things that could go wrong, the expression
"safety first" really applies.


Martin McCormick   amateur radio WB5AGZ    Oklahoma State University
Computer Center    Data Communications Group    Stillwater, OK