Security tags…how do they work ?

I’m trying to find out how do those security alarm tags work when strapped to a piece of electronics.I’m talking about the ones that have four straps going around the item and beep if cut loose. On second thought, what are they called anyways ?

They’re called “anti-theft alarms”. And they generally have a built-in battery and sounder. The sounder can be triggered several different ways, though not all models have all features:

1) Some of them have an anti-theft strip inside them. This strip is designed to set off the store’s anti-theft alarm at each door. Because the strip is inside the large plastic tag, you can’t just remove the strip from the tag.

2) Some of them have a vibration alarm. If the tag is designed to be on a device that doesn’t move, this is usually enabled. Though if it’s on a long cord so that you can move it around, the vibration alarm will be disabled. This will set of the alarm if you try to pry the device off its mount or walk with it.

3) If they’re attached to a fixed point, there will be a wire or wire loop. The exact design depends on the alarm type, but the basic idea is that you cannot cut cord between the device and its display.

4) They also will have some kind of device to prevent you from detaching the tag from the thing it protects. Two styles of this protection are common.

The strap type has a strap that wraps around the item and is then locked by a key. The strap is tight enough that you can’t slip the item out. There is a small wire in the strap that sounds the alarm if cut.

The plunger type has a small plastic button that is pushed out by a spring. When the tag is stuck onto the item to be protected, the button is pushed in and held in by the tape holding the tag in place. If you pry the tag off the item, the spring will push the button out, triggering the alarm.

A strip and plunger is usually sufficient protection for most items. With the strip, you can’t take the tag out of the store. With the plunger, you can’t leave the tag in the store and take the item.

For displays of things like digital cameras, the alarm system is usually in the table. Each digital camera has a wire loop to a plunger on the camera. Cut the cable and the alarm sounds because you broke the wire loop. Pry the tag off the camera and the plunger breaks the wire loop circuit, also setting off the alarm.

Some stores will slip an anti-theft strip (that sets off the alarm at their doorways) inside a display item such as a digital camera.

Jason & Elizabeth 4/16/08 Scenes

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