Like other EAS technologies, swept-rf uses a transmitter to create a surveillance are where tags and labels are detected. The transmitter sends a signal that varies between 7.4 and 8.8 Mhz (millions of cycles per second), which is why it is called swept; is sweeps over a range of frequencies.
The transmitter signal energizes the swept-rf tag or label, which is composed of a circuit containing a capacitor and an inductor or coil, both of which store electrical energy. When connected together in a loop, the components can pass energy back and forth or “resonate”. The frequency at which the circuit resonates is controlled by matching the storage capacity of the coil and capacitor. The tag responds by emitting a signal that is detected by a receiver. In addition to the small tag signal, the receiver also responds to the much larger transmitter signal. By detecting a phase difference between these two signals, and other properties of the tag signal, the receiver recognizes of a tag and generates an alarm.
