Abstract: An improved identification system that employs a novel radio frequency (RF) transponder. The RF transponder comprises a plurality of integrated circuit transponder chips, an RF transmit antenna coupled to an RF output of each of the transponder chips, and a sensor coupled to each of the plurality of transponder chips. A sensor switch is coupled between each of the transponder chips and the RF transmit antenna. The plurality of transponder chips may be individually programmed with different information, or identical information except for one bit. A code reader is coupled to an RF receive antenna for processing data transmitted by the transponder. The transponder is used to transfer information to the code reader relating to an item to which the sensor or transponder is coupled and the condition of the sensor switch. Transmission is accomplished by way of an RF communications link using the RF transmit and receive antennas.

Abstract: A passive integrated transponder (PIT) is attached to or embedded in an item to be identified. It is excited via an inductive coupling from an interrogator. The PIT responds to the interrogator via the inductive coupling with a signal constituting a stream of data unique to the identified item. The signal is in the form of two different frequencies, a shift from one frequency to the second during a bit cell representing a data "one", and a shift from the second frequency to the first frequency representing a data "zero". The responsive signal is then detected and processed for utilization in a data storage or display device.