| 摘要 |
The state (normal, alarm etc) of the mobile units attached to the goods is described in terms of the presence or absence of a response signal (421-423) over a transmission period (43), which is divided up into at least two parts (46,47) in which the mobile unit transmits its response signal. Transmission of this response signal is carried out in one or some parts of the transmission period, either individually on the same channel, frequency or the like, or simultaneously on e.g. different channels, frequencies or the like, or by the absence of a response signal. Information relating to e.g. monitoring, making an inventory or identification of objects within at least one monitoring region is carried out using a system comprising at least one central unit and a number of mobile units attached to the objects. The mobile units can collectively and/or individually receive enquiries in the form of labelling signals (45) or the like in a carrier wave (41) comprising radiation or the like emitted by an energy generating device. The mobile units send response signals to the central unit, which carries out a subsequent absence check. An Independent claim is also included for the system used to carry out this method. |
