Acoustic-Magnetic EAS systems transmit a magnetic frequency signal at a frequency of 58 KHz in a pulsed pattern. The transmitted signal is then used to energize an acoustic-magnetic retail security tag or label that is within the systems detection zone or field. While the transmitted signal is switched off between pulses, a narrow band receiver circuit within the electronics pack of the system then detects the retail security tag or label signal. 
A microcomputer within the system is then used to check the retail security tag or label signal that has been detected by the receiver, to ensure the following: 
•    The signal is radiated at the right frequency and has defined characteristics.
•    The signal occurs at a precise point in time, which is also synchronised to 
the transmitter.
•    The signal has been received at the proper level, and at the correct repetition 
or pulse rate.
If all the above criteria are then found to have been met several times in a row, only then will an alarm occur. This unique tag or label signature and also the large tag signal produced by the AM technology EAS system, enables it to achieve a wide surveillance area coverage, high tag or label detection rates, and also provides immunity to false alarm situations. 
The new acoustic-magnetic system has the ability to protect wide exits and allows for high-speed label application, uses a transmitter to create a surveillance area where retail security tags and labels are detected. The transmitter sends a radio frequency signal in pulses, which energize a retail security tag in the surveillance zone. When the pulse ends, the retail security tag responds, emitting a single frequency signal like a tuning fork. While the transmitter is off between pulses, the retail security tag signal is detected by a receiver.