| 摘要 |
A sensor for remote detection of objects in a surveillance zone (10) is preferably intended to be used in an article surveillance zone, which further has at least one transmitter means (11, 13) and at least one receiver means (12, 15) for transmitting and receiving, respectively, electromagnetic radio-frequency signals in the surveillance zone, and at least one modulating means (16) for generating a modulation field in the surveillance zone. The sensor is arranged to transmit an electromagnetic reply signal at the reception of electromagnetic energy from the transmitter means, said reply signal being dependent on the modulation field and being receivable by the receiver means. A magnetic element (23) is arranged in a sensor body (21; 101, 102), the magnetic properties of the element being controllable by a magnetic field acting as the modulation field, wherein the amplitude of the reply signal from the sensor is controllable through the magnetic modulation field. |
