Patent ID: 7548153

Claim:
An interrogation system for communicating with a plurality of transponders having different communication protocols, the interrogation system comprising a plurality of interrogators and a synchronization signal, each of the interrogators comprising a transmitter and a receiver the transmitters being arranged for transmitting downlink signals in accordance with different communication protocols over a downlink communications link to the transponders, the receivers being arranged for receiving respective uplink signals over an uplink communications signal link from the transponders, the synchronization signal being arranged for synchronizing the downlink signals for each of the plurality of interrogators, each of the interrogators operating in response to the synchronization signal to simultaneously transmit the downlink signals to the transponders to enable the transponders to provide their respective uplink signals after the transmission of the downlink signals, thereby enabling communication between respective ones of the interrogators and transponders without interference between the uplink signals from the transponders and the downlink signals from the interrogators.