Transponder communications device

A transponder communication device has an interrogation signal generator for generating an interrogation signal, a transmitter for transmitting the interrogation signal to a number of transponders, and a receiver for receiving answers signal from transponders. A transponder has an interrogation signal detector, an answer signal generator, and a state setting controller for setting a state of the transponder. The transponder communication device selects a single transponder from the number of transponders. First, the transponder communication device transmits an initial interrogation signal is transmitted to all transponders when the transponders are in an active state. In dependence of answer signals received from the transponders, the transponder communication device transmits a standby setting signal to at least one transponder at a time to instruct the transponders to adopt a standby state. In the standby state the transponders wait until a single other transponders has been selected. Thereafter all unselected transponders are selected by first setting the unselected transponders into an active state, from the standby state. Selected transponders are set into a passive state until all transponders have been selected. Thereupon, the active state is restored for all transponders.