[FoRK] Disruptions: Fliers Must Turn Off Devices, but It's Not Clear Why

Sean Conner sean at conman.org
Tue Dec 6 08:36:49 PST 2011

It was thus said that the Great Stephen Williams once stated:
> Fake security & false risk aversion, not to mention outright institutional 
> lying, bugs me.
> Disruptions: Fliers Must Turn Off Devices, but It's Not Clear Why. 

  The issue not be with avionic interference, but actual cellular network
issues.  It's pretty interesting how cell phones "work" with respect to the
phone network.  Each cell phone has what is called a "home switch".  When a
cell phone moves out of range of the "home switch", it syncs up to whatever
switch is nearby (i.e. what the cell phone towers talk to); that phone
switch will assign a temporary phone number to the cell phone, and send a
message to the "home switch" indicating the new number.  Someone calling a
cell phone will have the message routed to the "home switch", which will
then send a message back saying "call this number instead".  A similar trick
is used when making calls from a cell phone on a non-"home switch." You will
never see these temporary numbers.

  Now, it could be that during ascent, a cell phone can suddenly "see" more
towers than normal with signal strengths changing rather quickly and thus,
the cell phone network could get jammed with scores of messages handing off
cell phones from tower to tower until the airplane gets out of cell tower
range (I suspect cell phones need to be within a mile or two of a tower,
where as commercial jet planes fly higher than that).

  While this can explain turning off cell phones, it doesn't explain other
electronics (as a kid in the 80s, I was told to shut off a hand-held
electronic game I was playing just prior to take off).

  -spc (Or maybe airlines force the issue out of spite)

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