The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 31, 2006
Filed:
Aug. 27, 2002
Eric Perraud, Tournefeuille, FR;
Michel Burri, Le Grand-Saconnex, CH;
Eric Perraud, Tournefeuille, FR;
Michel Burri, Le Grand-Saconnex, CH;
Freescale Semiconductor, Inc., Austin, TX (US);
Abstract
A method of passive response communication, especially for an access control system, in which a first transponder () transmits an interrogation signal to a remote second transponder (), which responds by transmitting data back to the first transponder (), the two transponders each comprising a transmitter and a receiver, and a communication signal exchanged between said transponders () in at least one direction including a plurality of anti-relay-attack pulses (). At least one distinguishing pulse () selected among the anti-relay-attack pulses has a distinctive shape and the receiver of said communication signal is selectively responsive to the shapes of said plurality of pulses (). Interception of the transmitted signal in a relay attack using digital transceivers will not relay the distinctive shape and the response of the second transponder is inhibited.