[Asterisk-Users] WiFi IP Phones

[trixter http://www.0xdecafbad.com]

Given that they are radio transmitters, there is always the risk that
they can cause a spark and ignite something.  Additionally, reports have
happened of the battery itself getting shorted when removed and causing
everything from bullets to other explosive situations to occur.  When
you short the metal contacts on the battery it gets very hot, that heat
can cause things to ignite (gasoline for example needs about 500 degrees
farenheight to ignite).

Cell phones are normally upto 600mW PEP (max FCC allowed for a
handheld).  Wifi devices are normally upto 200mW PEP.  Amplifiers can
change this.  ETSI in europe limits to 100mW PEP and in Japan wifi is
limited to 10mW or something silly.  Thus its less of a concern in other
regions.

If you put a little bit of metal in the microwave you will see sparks on
the metal.  This is because there is a difference in RF potential across
two points, and an arcing occurs.  Granted most microwaves are 600-1000W
PEP, or 1000+ times the power, but the same type of situation can occur
if conditions are right.

In short there is no way to completly reduce the chance of explosions of
certain substances, to get a cell phone far enough away to mitigate that
danger is a matter of inches (1 inch == 2.54 cm), a wifi device, having
less power, is an even shorter distance.  If you are very near dangerous
substances that could be set off this way you should (hopefully anyway)
be trained in proper procedure there.

There is more risk (I think anyway) of filling a plastic gas can inside
a pickup bed with a plastic liner (plastic on plastic can create a
static discharge).  Cigarettes often dont get hot enough to ignite
gasoline (outside movies) because only when inhaling do they near hot
enough, just tossing one onto gas its normally 50 degrees below the
flash point.

Remember liquids dont burn, only gasses do in normal physics anyway
(special conditions can occur with extreme temperatures and pressures).
Gas station tanks are grounded if metal, the pumps certainly are.  This
further mitigates risk.

AFAIK there arent regulations that require them to prevent explosions,
any regulations like that would be on the devices that contain or
transport such materials that are likely to explode.  Because people
transmit a lot of power on mobile radios, those working with detonators
at construction sites often are required to put out signs saying 'dont
transmit explosive danger' because you can cause a false fire signal to
be sent to the detonator if you kick out enough power, but even those
devices are typically shielded to minimize this risk.



On Fri, 2005-06-17 at 10:49 -0400, Daryl G. Jurbala wrote:
> > -----Original Message-----
> > From: asterisk-users-bounces at lists.digium.com 
> > [mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of 
> > Anton Krall
> > Sent: Wednesday, June 15, 2005 3:01 PM
> > To: 'Asterisk Users Mailing List - Non-Commercial Discussion'
> > Subject: [Asterisk-Users] WiFi IP Phones
> > 
> > Guys.
> > 
> > I know there are wifi sip phones out there but I have a 
> > question, are any of these phones "anti explosive"? By that I 
> > mean, there are certain regulations about phones or cel 
> > phones that are not recommended to operate in environments 
> > like gas stations due to sparks and the chance of ingiting gas fumes.
> 
> You are referring to (in the US anyway) certification as "intrinsically
> safe".
> 
> I don't know either way about phones listed as such, but with the right
> terminology you might have better liuck searching.
> 
>  voiceverified.     | Daryl G. Jurbala
>  --------------     | Chief Technology Officer
>                     | 215.862.1160 x235 (Office)
> It had to be you!   | 215.862.9880 (FAX) 
> 
> 
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-- 
Trixter http://www.0xdecafbad.com     Bret McDanel
UK +44 870 340 4605   Germany +49 801 777 555 3402
US +1 360 207 0479 or +1 516 687 5200
FreeWorldDialup: 635378
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