Patent ID: 6992567

Claim:
An electronic label reading system, comprising: an interrogator including a transmitter for generating an interrogation signal and a receiver; a transmitter antenna connected to said transmitter for generating from said interrogation signal an interrogation electromagnetic field through which objects possessing code responding labels may pass; said code responding labels including receiving antennas for receiving from said interrogation field a label interrogation signal, said code responding labels being configured to generate label reply signals and, from said label reply signals, label reply electromagnetic fields; and a receiver antenna connected to said receiver for receiving said label reply signals from said label reply fields, said receiver being configured to detect and decode the label reply signals; wherein said interrogation field and label reply fields provide a communication channel from said labels to said interrogator; said interrogator is configured to transmit reply enabling signals to said labels before said labels are enabled to reply; each label reply signal contains a precursor portion separated from a remaining portion of the label reply signal by a predetermined gap; and further signals from said interrogator determine which labels of all labels present in the interrogation field that have replied with the precursor portion are enabled for further communication between themselves and said interrogator.