Radio Frequency (RF) Systems are the most widely used systems in the United States today and RF tags and labels are getting smaller all the time. As you can see in the drawing at the right, the RF EAS system works like this: A label -- basically a miniature, disposable electronic circuit and antenna -- attached to a product responds to a specific frequency emitted by a transmitter antenna (usually one pedestal of the entry/exit gate). The response from the label is then picked up by an adjacent receiver antenna (the other pedestal). This processes the label response signal and will trigger an alarm when it matches specific criteria. The distance between the two gates, or pedestals, can be up to 80 inches wide. Operating frequencies for RF systems generally range from 2 to 10 MHz (millions of cycles per second); this has become standard in many countries. Most of the time, RF systems use a frequency sweep technique in order to deal with different label frequencies.

Sometimes both the transmitter and receiver are combined in one antenna frame -- these are called mono systems and they can apply pulse or continuous sweep techniques or a combination of both. According to Tag Point Ltd. experts, mono systems could be effective for you if your store's entry is small. The mono system is used with hard labels, which are slightly more expensive than paper labels used with RF sweep techniques.

Sensors (gates/pedestals) made by Checkpoint Systems, one of the largest manufacturers of EAS products, emit a low-energy RF pulse, which "listens" for the tag. This technology, known as digital signal processing, actually "learns" about its surroundings so that it can accurately distinguish between the tag signal and extraneous noise. Store employees love this because it virtually eliminates false alarms! (Store owners often ask why there are no invisible sensors. Cross Point experts say it is technically possible to create an invisible system by, for example, installing an antenna loop around a store's door. However, tests have shown that the preventive value of a visible system is greater and results in decreased theft.)

There are many different ways to implement an RF system (see this patent and the patents it references for one type of implementation). The basic idea is that the tag has a helical antenna etched from thin aluminum bonded to a piece of paper. At the end of the antenna is a small diode or RC network that causes the tag to emit a radio signal in response to the radio signal it receives. To disarm the tag, a strong RF pulse (much stronger than the gates emit) blasts the tag and burns out the diode or RC components. Between the gates a burned out tag does not emit a signal, so the gates let it pass without an alarm.

As its name implies, source tagging is the embedding of disposable RF security labels at either the point of manufacture or packaging. Source tagging has been highly successful in the packaged products industry, and retailers, such as discount giant Target, are starting to use it for merchandise such as earrings, apparel, shoes, batteries, videocassettes, audiotapes, computer software, sporting goods and electronics. (Retailers' interest in source tagging has increased as shoplifters have gotten around anti-shoplifting tags applied to the outside of packages by removing the product and leaving the empty box on the shelf!)

The newest source tags are paper-thin and easily integrated into automated production processes. These tags are applied in primary packaging (or within or on the product itself -- for example, incorporated into woven garment tags) and under labels on bottles. Checkpoint experts say their two-dimensional source tags can be invisibly embedded between layers of thin paper stock or cardboard on standard blister packages. These invisible tags, which are deactivated by the clerk with a verifier that needs no physical contact with the tag to work, are especially effective at addressing employee theft and represent a hot topic in retail security today.

Sensormatic Products says its tiny Ultra-Strip can be detected through foil, liquids or layers of packaging. (Some industry consultants question the future of source tagging in retail apparel in light of the large number of existing microwave EAS systems -- systems that some consider obsolete and that cannot be adapted to incorporate low-cost source tagging in the future. There are also questions about how best to incorporate source tagging without losing the tag's inherent value as a theft deterrent.

Magnetic tags are made of a strip of amorphous metal, also called metglas which has a very low magnetic saturation value and this strip is also lined with a strip of ferromagnetic material with a moderate coercive field (magnetic "hardness"), except for permanent tags. Detection is done by sensing harmonics and summ or difference signals generated by the non-linear magnetic response of the material under a mixture of low-frequency (in the 10 Hz to 1000 Hz range) magnetic fields.

When the ferromagnetic material is magnetized, it biases the amorphous metal strip into saturation, where it no longer produces harmonics. Deactivation of these tags is therefore done with magnetization. Activation requires demagnetization. Due to the convenient dimensions of the tags, and their very low cost, this system is popular in libraries and retail stores. Magnetic systems are often referred to as 'Electromagnetic' (or EM) systems. EM systems rarely appear in retail .

Now the majority products in the market are DR (dual resonators) and LE (single resonator) sold by Sensormatic Electronic Corporation. our AMlabel has both three resonators and dual resonators . From the detection performance and aging stability point of view, our AM label is the alternative to DR label. However. Our AM labels are designed to have better deactivation performance because our AM labels use a soft magnetic bias instead of a semi-hard bias material that is used in DR and LE labels.