EAS systems operate from a simple principle regardless of the manufacturer or the specific type of technology used: a transmitter sends a signal at defined frequencies to a receiver. This creates a surveillance area, usually at a checkout aisle or an exit in the case of retail stores. Upon entering the area, a tag or label with special characteristics creates a disturbance, which is detected by the receiver. The exact means by which the tag or label disrupts the signal is a distinctive part of different EAS systems. For example, tags or labels may alter the signal by using a simple semi-conductor junction (the basic building block of an integrated circuit), a tuned circuit composed of an inductor and capacitor, soft magnetic strips or wires, or vibrating resonators.
By design the disturbed signal created by the tag and detected by the receiver is distinctive and not likely to be created by natural circumstances. The tag is the key element, for it must create a unique signal to avoid false alarms. The disturbance in the electronic environment caused by a tag or label creates an alarm condition that usually indicates someone is shoplifting or removing a protected item from the area.
The nature of the technology dictates how wide the exit/entrance aisle may be. Systems are available that cover from a narrow aisle up to a wide mall store opening. Similarly, the type of technology affects the ease of shielding (blocking or detuning the signal), the visibility and size of the tag, the rate of false alarms, the percentage of detection rate (pick rate), and cost.
The physics of a particular EAS tag and resultant EAS technology determines which frequency range is used to create the surveillance area. EAS systems range from very low frequencies through the radio frequency range. Similarly, these different frequencies play a key role in establishing the features that affect operation.