An electronic label reading system includes an interrogator including a transmitter
and a receiver. The system also has a transmitter antenna connected to the transmitter
for generating an interrogation electromagnetic field through which objects possessing
code responding labels may pass. The code responding labels include label receiving
antennas for receiving from the interrogation field a label interrogation signal,
and generate label reply signals, and, from the label reply signals, reply electromagnetic
fields. The system also has a receiver antenna connected to the receiver for receiving
the reply signals from the label reply fields. The interrogation field and label
reply fields provide a communication channel from the labels to the interrogator,
and the interrogator signals to the labels condition information indicative of
the condition of the communication channel.