Patent ID: 6946951

Claim:
A system for interrogating electronic labels, including: (a) one or more electronic labels, each attached to an object, (b) an interrogation device providing an interrogation field using an interrogation signal, (c) the interrogation signal containing information in the form of a plurality of symbols encoded into the interrogation signal, each symbol being represented in the form of at least one time interval between consecutive dips in amplitude of the interrogation signal, each time interval having a value selected from a finite set of values such that the ratio of any given time interval value to any smaller time interval value exceeds a predetermined amount, wherein an electronic label located within the interrogation field detects and decodes the interrogation signal to obtain the symbols, the electronic label also deriving electrical power from the interrogation field to interpret the recovered symbols and generate a reply signal, the reply signal being detected and decoded by the interrogation device, and wherein the predetermined amount exceeds an amount determined from a frequency variation of the electronic labels, the frequency variation being caused by a variation in the electrical power.