Patent ID: 6377176
Filing Date: 2002-04-23
Classification: G06K,G08B,H01Q

Abstract:
A radio frequency identification (RFID) system, comprising:a) an RFID reader generating an electromagnetic field at a predetermined frequency, said RFID reader having sensing means that interfaces with an external access control system for sensing a data polarity requirement of said external access control system, and to configure an output of said RFID system to conform to said polarity requirement, said RFID reader further comprising pre-compensation means for substantially eliminating changes to an RF field caused by influences of metal proximate said RFID reader; and b) an RFID transponder that interacts with said electromagnetic field of said RFID reader, said RFID transponder containing an ID code associated therewith, and wherein said RFID transponder has means for disrupting said electromagnetic field of said RFID reader, whereby said ID code is transmitted to said RFID reader as a data stream comprising a preamble of imbedded data and at least two data bit groups, each of which has a parity bit.