Last Monday I was flying to Scotland for a few days to have a chat with a few of our customers up there. I thought I would show them due respect so on Sunday afternoon I popped into Marks and Spencer and bought a new suit. When I got home I set to making our Sunday roast dinner so didn't think about the whistle until about eleven that night when I went to pack. To my annoyance I found this bad boy attached to the arm. Clearly the assistant in the shop had missed it when he was putting the suit in a bag for me.
At first I wasn't too bothered. After all - it would just take a bit of brute force to rip it off and all would be well for the morning. However, when I looked at the other side - my heart skipped a beat.
What at first look like a simple dongle to trigger an alarm at a security gate was in fact an ink tag. I immediately started thinking of the paint bombs that are placed in bags of money to prevent theft! Was this device explosive? Was it dangerous?
I soon came to my sense. Of course Marks and Sparks aren't going to try and blow up their customers. That would be very bad for business. The device must be passive. But I was still left with a dilemma. It was eleven o'clock at night so I couldn't go back to the store to remove it and I was flying first thing so couldn't pop into the shop in the morning either. My other suit was at the dry cleaners so I had no option. I had to figure a way of getting it off without covering myself and my new suit with ink.
Obviously being a geek, my first step was to check on the Internet to see if there were examples of how other people had done this. I was very surprised to see that there was so little information and what there was involved power tools to break the "clip" part of the device so that it would release the pin that connected it to the ink container. This seemed like massive overkill to me. Isn't the obvious weak point the pin?
So I went and assembled the vast array of tools that I would require to crack the device.
Firstly I just ripped off the cardboard notice which meant there was just enough room to get my snippers in. I was being as gentle as I could because this was obviously putting pressure on the ink container.
I don't know what the pin is made of, but it certainly took a fair bit of effort to eventually snip through it. Let me be very clear at this point just for in case you are an aspiring shop lifter and think I have just described how to deactivate security devices. I have no idea how close this came to releasing the ink all over my hands and suit. I only attempted this because I had no choice and was probably emboldened be a few glasses of red wine during dinner. If you try this you will be covered in ink and caught by the store detective who will throw you in jail! Crime doesn't pay.
Any way. That was it. The top was off
The device was off the suit and I was able to fly off to Scotch Land the next day in my fine new dapper suit. The story could indeed have stopped there.
However, I was curious about the ink device. How did it work and what would it do? On my return from Scotland the only thing on my mind was experimenting! As you can see below there appear to be two glass vials, one containing blue liquid and the other yellow.
I put the device in a plastic bag to prevent making a mess and tried to pry the top off using a screw driver.
I didn't have any luck pulling the top off so I decided to get a bit more agricultural and just smashed my way in. This enabled me to see that the mechanism couldn't be any simpler. The pin is connected at the bottom to a disc which would be pulled up if pressure where exerted smashing the glass vials of ink. I wonder how close I came when cutting the pin?
I pulled the pin with a pair of pliers and the yellow vial smashed very easily releasing the ink.
Tipping the bits out it is clear that there is quite a bit of yellow ink in there. You can also see the pin and disc much more clearly.
Here is the blue ink vial. It was not broken because I had smashed the case so there was uneven pressure on the two vials. If the device had been intact then they would both have been released at the same time.
Here is the blue vial after I had cleaned the yellow gunk off it. Can you guess what TV program I'm watching as I push forwards the bounds of ink tag science? It's "Heroes" which is meant to be the new "Lost" apparently.
The blue vial was going to have to be smashed as well so into the bag it goes.
Splat! A very gentle tap with the screw driver handle and the second vial is a goner.
There appears to be more of the blue ink that there was of the yellow. It also seems to be of a thinner consistency - in fact just about the consistency of ink you would use in an ink pen.
I can only speculate that the designers chose to use yellow and blue since that would enable the device to be used with any coloured garment. The blue might not have shown up very much on my blue suit but the yellow certainly would. Unless you were stealing a Hawaiian shirt it is a very efficient deterrent.
Finally, just to reiterate, I was lucky. Don't try this unless you have no choice and don't mind getting ink on your hands and cloths.
UPDATE: 9th March 2007
Some cheeky anonymous monkey left the following comment: "Hang on.... surely a *real* geek would also dismantle the other half to find out what's holding the other end of the pin? Inquiring minds need to know!"
So another dig into my tool chest produces my little pen knife. I start hacking away at the case.
It's quite tough but after a few minutes I'm making headway.
Result! I prise the two half's apart to find this fella inside. Hmmm. Still none the wiser.
I'm expecting some great revelation when I separate it from the case - but no.
There is a metal bit at the bottom but the rest is covered by the second plastic cover.
What I do find quite interesting is that the remaining bit of pin cannot be removed by pulling it from the bottom (obviously) but it can be very easily be removed by pulling it from the top. Of course this makes sense because the pin needs to be inserted easily when it is still attached to the ink tank but how is this being achieved? I expected to see a notch or some such indentation on the pin which would be caught by some sort of one way catch - but I'm wrong. That isn't how it works.
When I remove the second cover I'm even more confused. What is with the spring! How does this thing possibly work?
Here is the metal bit disassembled. Note that the four ball bearings sit inside the brass coloured sleeve. I have rested them against the pin to stop them rolling away.
Finally - the whole top bit shown disassembled. Note that there doesn't appear to be any transmitter or RFID or anything like that to trigger an alarm. I think that this device is just an ink tag and not designed to do anything else. I guess this is why the alarm didn't go off when I left the store.
Oh! So you want to know how it works as well? OK here is the secret. And I must say it is mighty smart. The ball bearings sit in the sleeve as mentioned above. As you can see there is only just enough room for them.
When you insert the pin the bearings become cramped. If you try and pull the pin downwards it is prevented from moving because of the friction from the bearings. They have nowhere that they can go. However, if you pull the pin from the top it works fine because the ball bearings can move upwards releasing the pin.
So by placing a washer and spring on the top (see the previous disassembly photo) it means that you have a nice enclosed unit that will only let a pin pass through it in one direction. However, the ball bearings are magnetised, so at the checkout the dongle can be placed inside a powerful ring magnet that will pull the bearings slightly upward against the force of the spring releasing the pin. Clever.
Update 22nd April 2007.
Who would believe it - it's only happened again! Not an ink tag this time - just an ordinary one. Watch and learn ... http://www.mrports.com/2007/04/remove-security-tag-redux.html