L5 sets off store security sensors?

picked up an l5 from tactical warehouse. decided to stick it in a jacket with lots of pockets because the weight was barely noticeable.

walked into a brooks brothers and a gap today. the security alarms went off as soon as i walked in the door. they didn't go off when i left. dropped the l5 off in the car and walked into both stores again and the alarms didn't sound.

i can't edc an l5 without causing a racket in every store i visit? /ubbthreads/images/graemlins/help.gif

Well...Most store security sensors work off of acousto-magnetic technology. The sensors contain two disimilar metals, and when the sensor is passed through the gates, a magnetic field is produced between the two metals, and this field is detected by the sensor gates, setting the alarm off. Some cell phones and especially older beepers (pagers) set the gates off, depending on the sensitivity level.

--dan

The alarms would probably be set off by any large metalic object that could be the general size and weight of a small hand gun. I doubt it was anything special about the L5.

You might see if Surefire would build you a special light made of titanium, it supposedly has a much smaller magnetic signature /ubbthreads/images/graemlins/grinser2.gif

I left a few "secrets" out of my description, but unless the gates aren't calibrated properly, large metallic objects won't set them off.

Hell, no one pays attention to 'em anyways!

--dan

[ QUOTE ]
FlashlightOCD said:
The alarms would probably be set off by any large metalic object that could be the general size and weight of a small hand gun. I doubt it was anything special about the L5.

You might see if Surefire would build you a special light made of titanium, it supposedly has a much smaller magnetic signature /ubbthreads/images/graemlins/grinser2.gif

[/ QUOTE ]The electronic loss-prevention measures used at retail establishments aren't metal detectors, which is essentially what airports use. If they were, no one could walk out of Wal-Mart with a purchased toaster or pipe wrench.

Anyhow, I wasn't going to say anything until I read this thread, but twice now I've set off the alarm at Target, both entering and leaving the store. I had my L4 with me on both those occasions, and only on those occasions. Security has always waved me through. I think tomorrow I'll go back to Target with my L4 and attempt to verify if indeed it is setting off the alarm.

There are tricks (I assume these are the 'secrets' Dano left off) that can be used to get around merchandise loss prevention systems. Perhaps these will have to be applied to the L4.

Still slightly off topic: The newest systems can't be defeated by aluminum (an old shoplifter trick). Probably there's something in the L-4's like the pager issue which was the small amount of shielding and the circuit boards mimmicking the sensors, and fooling the gates for a false positive.

--dan

The regulator circuitry in the L4, L5, (L6?) could be triggering some systems. I wouldn't let the security folks "deactivate" your regulated LED though. See:
http://electronics.howstuffworks.com/anti-shoplifting-device.htm

now what you need to do is buy an m2 to see if that sets off the systems /ubbthreads/images/graemlins/wink.gif

I didn't know about the aluminum trick until I saw an episode on COPS. Thanks COPS. /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/whoopin.gif

note to self:
criteria for edc - must be able to pass security sensors undetected

guess i'll have to stick with the arc lsh-p in my pocket

So only regulated lights will cause problems? What about DD lights then? I assume they'd be fine.

There are two types of anti-theft detector. The older one was using a resonant circuit (a coil with a capacitor in parallel) embedded in the store item. This type was defeated with aluminium foil wrapped around the item stealed from the store.
The newer type uses, as Dano said, two acoustically resonant high-carbon steel blades. The "sensor" is neutralized at cash with a strong magnet, that sticks the two blades togheter.
The detector "gate" uses a dumb FET gate-dip circuit, that can be set off by any abnormal electric field variation, like the one produced by any amount of high resistivity material: try to walk trough the gate with a pouch full of powdered copper. The "mix" of special aluminium alloy of SF lights, that can well contain some magnesium, the anodizing and the number of threading (4, in the L4) together with the steel casing of 123 cells, may set off the alarm in a non-properly aligned anti-theft detector. Or there is something resonating, inside the L4, at the "sensor" frequency...

Anthony

I don't really understand why the internal electronics would matter at all.
To the security system the L5 is essentially an aluminum tube. Such a tube should appear like a Faraday cage and block any RF signals that are trying to penetrate. Right?

Maybe TheProphet is on to something with the alloy and geometry of the tube itself......

I know of 2 different kinds of Sensor's.

The first one I'm thinking of is along the lines of TheProphet's description and takes a magnetic pad to deactivate the sensor. I assume it magnetizes the metal stripes so they wont set off the sensor.

The other type that we use at my workplace uses a square sticker with a metallic spiral on the bottom side with the adhesive. I am not quite certain how these get deactivated, but I know it does not involve magnetics.

I know both types of theses security devices can be found under the Sensormatic brand name.

I suspect they are both dependent on upon resonance. The sensor detects the re-radiation of the energy from the sensor.
One way to detactivate it is to make the sensor as two seperate parts, both resonate. Deactivation is accomplished by connecting
the two parts, which would halve the resonant frequency, and no longer re-radiate. The magnetic pad likely causes the two pieces to stick together, doubling the effective size of the elements and halving the resonant frequency.

the spiral ones are deactivated by exposing them to a strong rf field at its resononant freq which burns it open.
i got the guts from such a system and it has a rf power amp using 2 mrf 454's.great for ham radio .

The ARC AAA sets of the alarms of many stores here in Switzerland. I pay attention not to carry it when I go shopping. No such problems with the M2.

If the problem is not related to RF absorbtion due to the tube composition, it must be resonance.
It could be that the coil used in the L4 or the AAA has a resonance frequency close to the one that triggers the alarms. All the converters used in our lights oscillates in the ultrasonic portion of the spectrum. It is highly possible, IMO, that there is an harmonic, or sub-harmonic of the main frequency, that matches the specific frequency used from the alarm.
Must walk with a data logger thru that gates to understand why? At a certain point, I don't really care, since I am not shoplifting...
If somebody has an old style grid-dip or gate-dip meter, it would be easy to find out the resonance frequency of the L4 or the AAA.

Anthony

P.S: Note for MicroE: you are right, but... consider an acoustical stimulation on a diapason, that in turn "answers" with a electromagnetic wave... do you recall the old-age Bulova diapason watches?

I carried an L4 as my EDC for 5 months and never set anything off.