DIGITAL COMPACT DISC PLAYER SECURITY SYSTEM REPRODUCING METHOD AND APPARATUS

摘要

A SECURITY SYSTEM FOR PREVENTING DISC (1) PLAYERS FROM BEING USED WITH UNAUTHORIZED SOFTWARE IS DISCLOSED. THE SECURITY CODE IS STORED THROUGH MODULATING AN OFFSET OF THE PHYSICAL POSITION OF A PLURALITY OF DATA BITS FROM A NOMINAL TRACK POSITION. A TWO PART OPTICAL READ HEAD PROVIDES AN RF SIGNAL CORRESPONDING TO THE PRESENCE OF A PHYSICAL OFFSET MODULATION. THE RF SIGNAL IS PRESENT WHEN THERE IS A PHYSICAL OFFSET OF THE DATA BITS DEFINING A FIRST LOGICAL STATE AND THE ABSENCE OF THE RF SIGNAL DEFINES A SECOND LOGICAL STATE. A DIGITAL SECURITY CODE IS ENCODED AND DECODED IN THIS MANNER. A SYSTEM FOR ENCODING A SECURITY CODE THROUGH MODULATING THE PHYSICAL OFFSET OF A PLURALITY OF DATA BITS FROM A NOMINAL TRACK POSITION IS ALSO DISCLOSED. (FIG.7)