No personal knowledge, but I had nothing better to do and did a little research ;-)

EAS is the proper name for anti-theft system. It stands for Electronic Article Survelliance.

How this is removed depends on the merchandise and the devices used.

For clothes and such "hard tags" are used. These are removed with a "detacher".
For books CDs ect. various types of labels are used. These are deactivated at the register with a "detuner"

I had trouble finding the correct term that would work for the removal system of both, but then I found it:

Magellan® 9500 and SmartSentry™ Scanning and EAS Deactivation ...
Contact the Pre-Sales Team. Magellan® 9500 and SmartSentry™ Scanning and **EAS Deactivation System**. High Performance Scanner/Scale ...
www.pscnet.com/html/mg9500.htm

and quite a few more googles.

And here is the additional information that helped me get there:

EAS Tag Removal device
http://www.magen.ca/toronto/systems/theft_control/photos/


EAS Tag - EAS Label | What is an EAS Tag?
... The three different types work only within their respective detection units. Also
Known As: EAS Tag. General Use: Electronic Article Survelliance (EAS). ...
retailindustry.about.com/ library/terms/e/bld_easlabel.htm - 36k - Cached - Similar pages

Hard Tag - EAS | What is a Hard Tag?
... What is a Hard Tag? Definition: A reusable EAS tag that is removed from merchandise
at the point of sale to be reused on other merchandise. ...
retailindustry.about.com/ library/terms/h/bld_hardtag.htm

Hard Tags, Detachers, Lanyards & Pins
... DETACHER, LANYARDS & PINS. Detacher: The attractive round chrome detacher allows for quick and easy removal of the hard tags from merchandise. ...
www.ilps.com/hard_tags.htm

Shoplifting prevention systems and accessories - Office Zone
... $70.00. Detacher for Shoplift Prevention Tags, The attractive round chrome detacher allows for quick and easy removal of hard tags from merchandise. ...
www.officezone.com/shoplift1.htm

http://universaleas.com/detachers.htm

Three types of EAS systems dominate the retail industry. In each case, an EAS tag or label is attached to an item. The tag is then deactivated, or taken from an active state where it will alarm an EAS system to an inactive state where it will not flag the alarm. If the tag is a hard, reusable tag, a detacher is used to remove it when a customer purchases the item it's attached to. If it's a disposable, paper tag, it can be deactivated by swiping it over a pad or with a handheld scanner that "tells" the tag it's been authorized to leave the store. If the item has not been deactivated or detached by the clerk, when it is carried through the gates, an alarm will sound.

It looks like the detectors cost about $1000-$2000. Labels are cheap, 2000 for about $100. The labels are deactivated using a "detuner" which costs about $300.

Detacher, Lanyards and Pins

Detacher
The attractive round chrome detacher allows for quick and easy removal of hard tags from merchandise. Its small size fits easily on even the busiest check-out counter.

Lanyards
Used with hard tags, lanyards protect merchandise which otherwise could not be protected. Some examples are: tennis rackets, stereo equipment, hardware items, and sporting goods.

Pins
These sturdy pins fasten hard tags to merchandise.



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Note added at 42 mins (2005-01-28 11:43:46 GMT)
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Sorry, the label section of the last site and the URL was cut off, so here it is:

Labels
We offer a variety of labels in the following sizes:

2\" x 2\" (50 x 50 cm)
1.5\" x 1.5\" (40 x 40 cm)
1.25\" x 1.5\" (33 x 40 cm)

These labels are available in several different frequencies including 8.2 MHz and 9.5 MHz. Their use depends upon the application.

Different printing options are also available.

Deactivators
Our deactivators are designed to deactivate all 8.2 MHz disposable labels. The operator does not have to find or locate the disposable label on the item in order for it to be deactivated. An audible tone alerts the operator of labels that will not deactivate. The deactivation unit is placed next to the point-of-sale equipment for quick and easy checkout.
http://www.controlelectronic.com/eas.htm