Patent ID: 7760677

Claim:
A method of communicating between an interrogator and one or more radio frequency identification (RFID) devices, the method comprising: placing the devices in communication range of the interrogator, wherein each of the devices accommodates a first predetermined number of bits to be used for a respective first value; causing the devices to select random values, wherein each of the devices chooses random values independently of random values selected by other devices; transmitting a signal from the interrogator requesting devices having first values within a specified group of one or more values to respond, the specified group being less than the entire set of values having the first number of bits; receiving the signal at the devices, and in response, each of the devices respectively determining if their respective first value falls within the specified group and, if so, sending a respective reply including a respective random value to the interrogator within a randomly selected time slot of a number of slots, and, if not, not sending a reply; and determining with the interrogator if collisions occurred between devices that sent the respective reply and, if so, adjusting the number of slots.