I read in sci.electronics.design that KLM wrote (in
) about 'Cellphones and
Bombs', on Fri, 19 Mar 2004:

To the objections from other posts; of course a determined terrorist
will always get through. Who can stop one who is willing to blow
himself up.

If he acts entirely alone, like the one who blew up the gay pub in
London, no-one, unless by chance - nail-bomb in Brixton.

But anyone who confides in others is vulnerable to infiltration, and
there's a lot of that going on, you can be sure.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

In article ,
Costas Vlachos wrote:

Yes, that is correct - at least that's what was said on the news channels
here in the UK. The Spanish bombs were triggered by mobile phones set on
alarm at 7:39am IIRC - the phones didn't even have to have SIM cards in
them. No signal jamming equipment could have prevented them from going off.

Ah - the modern equivalent of the classic alarm-clock timing
mechanism. Modern digital watches would work about as well.

As to the idea of jamming cellphone frequencies: even if physically
practical, and even if the government would authorize widespread
distribution of devices which jammed a licensed radio service
(doubtful IMO since the cellphone companies paid $$$ for their
licenses and would doubtless fight it in court), it would only move
the problem elsewhere. There are far too many radio frequency bands,
and far too much commonly-available equipment which could be modified
to allow for remote detonation control over moderate distances. Garage
door openers with rolling-code security, portable radios of all sorts,
etc. could all be incorporated into a scheme for remote- controlled
mass murder by those whose inventiveness and skills outweighs their
ethics and humanity.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"KLM" wrote in message
...
On Thu, 18 Mar 2004 16:53:28 -0800, "CW"
wrote:

Do you know what the word ILLEGAL means? It is very obvious that you are
ignorant of the technical details and I am not going to be your
electronics
teacher. It is illegal for a reason.


Terrorists are using cellphones to kill and maim hundreds of people
and you are maintaining that unrestrcted CP use is a god given
inviolable right.

Nope. He's simply pointed out, quite correctly, that willful
interference with a legitimate radio service is very , very illegal,
and it is so for some very good reasons.

Besides, "jamming" cell phones is a stupid and ineffective idea anyway.
You can't reliably "jam" such things within a limited area (which is one
reason for the laws in question - to RELIABLY jam phones within an
area that IS under your legal control, you MUST create signals that will
cause interference OUTSIDE that area. Hence, don't do it.) A far
better plan is to simply shield the area in question from ANY RF
transmissions - easily and relatively cheaply done, and will cause no
legal or other hassles, or unintended interference. And you can still
bring in any RF-based info you DO want - TV, radio, etc. - via a
cable.

Bob M.

In article ,
(The Captain) wrote:

Dave Shrader wrote in message
news:Xu36c.33004$po.292953@attbi_s52...
John Michael Williams wrote:

SNIP

However, the first radios transmitted
sparks, so in principle it should be possible to
transmit near a long wire separated by a small gap from
ground or another wire and get a small spark. So, I
decided to try an experiment.

SNIP

There is one other potential source for a spark that you did not
investigate.

A make/break contact in a switch causes sparks when opened. The US
Military specifies special shielded switches for their explosive, gas
vapor, etc., environments.

So, it is possible that pressing the PTT or the ON/OFF switch causes the
necessary spark. Remember the Apollo ground fire. A switch/spark caused
an oxygen explosion.

Actually, anyone who has worked in the offshore oil industry will be
familiar with the concept of intrinsic safety. This requires that no
electronic instrument shall be able to ignite a mixture of air and
inflamable vapour or gas. All handheld radios used on rigs are
intrinsically safe, making them far more expensive than the standard
variety.

I very much doubt that cell phones are buit to intrinsicly safe
standards, and under those circumstances I would certainly not feel
safe near someone yacking while filling.

So, an interesting querstion is; does your phone conform to UL
requirements for intrinsic safety? And if not, why are you using it
in an area where an explosive gas air mixture is possible?

Cap

Actually the electronic portion of the Intrisically Safe Radio is
the same as the regular Radio of the same model. What is different is
the Battery and the Battery Connections. On an Intriscally Safe Radio
the Battery and Battery connections are Specifically Designed so as
to not spark when changed, while the radio is turned on. This design
change isn't really that expensive, but the testing that is required to
receive the "Intrinsically Safe" Lable, is extremely expensive.

me

"KLM" wrote in message
...
Why not include a circuit in every cellphone that will cause the
answer bell to ring when anyone carrying a cellphone crosses one of
these interrogators. Maybe have the circuitry activate a different
ring tone or ring pattern from the normal call ring. Its extremely
short range and won't interefere with normal cellphone use.

Simple - again, the strong likelihood of interference with cell phones
AND other legitimate services. Plus the rather obvious fact that it
won't achieve the desired goal; once these things were placed into
service, it would be trivially easy for a "cell phone bomber" to disable
their phone's ringer. Or to cause a dummy ringer (the one that doesn't
have to do with the bomb) to go off and thus defeat the security.

You really should learn a bit more about how these things work before
proposing supposed "solutions" to the supposed "problem."

Bob M.

I read in sci.electronics.design that Me wrote (in Me-
) about 'CB Radios,
Cellphones and Gasoline Vapor Ignition', on Fri, 19 Mar 2004:
This design
change isn't really that expensive, but the testing that is required to
receive the "Intrinsically Safe" Lable, is extremely expensive.

There are strong suspicions in some countries that it is quite
unjustifiably expensive, because only a few facilities offer it. More
competition is required. Or a government investigation.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

KLM wrote in message . ..
On Thu, 18 Mar 2004 13:00:55 -0800, "CW"

And cellphone signal blocking is localized, short range, same as WiFi.
Put up a sign to that effect in your business premise. Those who feel
they must have their cellphone access 24/7 can always step outside
the door or avoid the place. That business will survive because there
are a miniscule number of 24/7 cellphone freaks.

Anyway the use of cellphones while driving is banned in many states in
the US and worldwide. What is so different in banning their use in
selected public places. The only difference is that signal blocking
is applied universally in that defined building area, and without
having intrusive checks being made on anyone to effect compliance.

To prevent the use of cellphones ANYWHERE kills an industry, I want to
be able to use it everywhere, OK handsfree in a car.
If the terrorist intention is to damage industry, economy, then yes.
Else live with the danger.
JP

"Reg Edwards" wrote in message
...
I AM old enough to remember the pre-war and the phoney-war impressions of
the population of the cities of Birmingham and Coventry about the
capabilities of the Luftwaffer.

It was "They'll never get this far."

At the same time the citizens of Cologne, Hamburg, Berlin and Dresden were
saying much the same thing.

Whath they found out was that they don't have to ALL get through.

"Bob Myers" wrote in
:

"KLM" wrote in message
...
On Thu, 18 Mar 2004 16:53:28 -0800, "CW"
wrote:

Do you know what the word ILLEGAL means? It is very obvious that
you are ignorant of the technical details and I am not going to be
your
electronics
teacher. It is illegal for a reason.


Terrorists are using cellphones to kill and maim hundreds of people
and you are maintaining that unrestrcted CP use is a god given
inviolable right.

Nope. He's simply pointed out, quite correctly, that willful
interference with a legitimate radio service is very , very illegal,
and it is so for some very good reasons.

Besides, "jamming" cell phones is a stupid and ineffective idea
anyway. You can't reliably "jam" such things within a limited area
(which is one reason for the laws in question - to RELIABLY jam phones
within an area that IS under your legal control, you MUST create
signals that will cause interference OUTSIDE that area. Hence, don't
do it.) A far better plan is to simply shield the area in question
from ANY RF transmissions - easily and relatively cheaply done, and
will cause no legal or other hassles, or unintended interference. And
you can still bring in any RF-based info you DO want - TV, radio, etc.
- via a cable.

Bob M.


Spot on, thats whats used where possible in sensitive buildings in the
UK.

The use of CP's for these purposes has been going on for 30 years at
least. It's not new and various means to counter it have been tried with
various success. There's a tendancy to assume these people are stupid as
well as socially corrupt. Not true. The IRA for instance used cp's in the
70's and 80's bombing of London and the mortar attack on 10 Downing
street while the cabinet was in session. The IRA's technique was to use
two cell phones and a sequence of calls to arm and trigger the weapon.
Once the bomb was placed and the phone was on and receiving signal the
bomb was also set to go off if the phone was switched off or the signal
lost - as it would be if the area was 'jammed'.

Jamming the phone service could actually set the thing off where the
planter wanted it to be. Not a good idea.

As an aside, given that Bush has started his war on terrorism, terrorists
and all that support them, does that mean he's going to pursue all those
who have and still do support the IRA and 'the cause' who where almost
entirely funded from the US?

Reg Edwards wrote:
"At the same time the citizens of Cologne, Hamburg, Berlin and Dresden
were saying much the same thing."

Yes. Hermann Goering boasted early in the war that his name was mud if
bombs fell on Berlin.

Later in the war as Hermann scurried for shelter he was heard
introducing himself as "Herr Mud".

Best regards, Richard Harrison, KB5WZI