How Does EAS Work?

Acousto-Magnetic (AM)

Acousto-Magnetic systems transmit a radio frequency signal at 58 kHz in a pulsed pattern. The transmit signal energizes an Acoustic-Magnetic tag in the detection zone. When the transmit signal pulse ends, the tag responds, emitting a very distinctive frequency signal, like a tuning fork.  While the transmitter is off between pulses the tag signal is detected by the receiver. A microcomputer checks the tag signal detected by the receiver to ensure it is at 58 kHz frequency, is time-synchronized to the transmitter, at the proper level and at the correct repetition rate. If all these criteria are met, the system alarm will occur.  This unique process provides immunity from false alarms.

Radio-Frequency (RF)

Swept-RF uses a transmitter to create a detection zone where tags 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; it sweeps over a range of frequencies. The tag responds by emitting a signal that is detected by a wideband receiver, meaning a receiver that monitors for signals over a wide frequency range; for swept-RF systems the bandwidth is typically about 1,400,000 Hz. By detecting a phase difference between these two signals, the receiver recognizes the presence of a tag, and it alarms.