| 摘要 |
A device for detecting and identifying wearable identification units (20) for users at a predetermined distance around a central station (2). The central station (2) has a transmitter (4) and a receiver (6) for electromagnetic signals and a control unit (8), which initiates the sending of a polling signal at predetermined time. The time may be based on multiples of intervals. Furthermore, there are a plurality of wearable identification units (20), which have a transmitter (22) and a receiver (24) for electromagnetic signals and a control unit (26), which is designed to initiate the sending of an identification unit-specific response signal by the transmitter (22) upon the reception of the polling signal after a time delay which is specific of the particular identification unit (20), wherein the identification unit-specific time delays of the plurality of identification units (20) are selected to be such that the response signals of no pair of identification units (20) will overlap when the pair of identification units (20) receives the polling signals of the central station (2). The control unit (8) of the central station (2) is designed to analyze the signal received after the sending of the polling signal and to determine the time between the sending of the polling signal and the reception of a signal in order to detect the presence of an identification unit (20) and to identify it based on the identification unit-specific response signal and based on the identification unit-specific time delay.
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