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:
Oct. 22, 2002
Filed:
Jul. 03, 2001
Thomas Reisinger, Regensburg, DE;
Siemens Aktiengesellschaft, Munich, DE;
Abstract
The invention relates to a method and apparatus for protecting a transmission path between a base unit and a mobile key unit in an access control system, in particular for motor vehicles. A carrier signal which is modulated with a user signal is transmitted from a transmitting unit to a receiving unit. According to the invention, a separate reference signal, which has a fixed phase angle with respect to the carrier signal, is also transmitted. The phases of the reference signal and of the carrier signal are compared in a test circuit, and an alarm signal is emitted if a phase difference which varies with time is found.
Data source: USPTO (United States Patent and Trademark Office) public patent records. Weekly synchronization. How IDiyas builds this profile