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. 21, 1992
Filed:
Mar. 15, 1990
Abraham Hoogendoorn, Eindhoven, NL;
Gerardus Lokhoff, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
Low-frequency components of the left and right channels of the audio signal to be recorded are derived by means of filters (3, 4). First and second auxiliary signals are added to such low-frequency components in such a way that during reproduction of the audio signal so recorded, including the first and the second auxiliary signals added thereto, by means of two loudspeaker units arranged in a stereo configuration, the two auxiliary signals are not audible. However, they will inhibit re-recording by apparatus for recording audio signals which are not copy-protected in the form of the aforesaid two auxiliary signals, or will cause such apparatus to indicate that the audio signal to be re-recorded is protected.
Data source: USPTO (United States Patent and Trademark Office) public patent records. Weekly synchronization. How IDiyas builds this profile