Playback apparatus with second variation detection

Abstract

The invention relates to a playback apparatus for retrieving information from an information carrier (). The information has been recorded on the information carrier () in the form of variations of a first physical parameter. The playback apparatus scans the information carrier by means of a transducer (), which is responsive to said variations of said physical parameter. An information recovering circuit () recovers the information from a first detection signal (D) received from the transducer (). The information recovering circuit () comprises a phase-locked loop (). The information carrier () exhibits a second variation of a second physical parameter, which differs from said first physical parameter but which is detectable by means of said transducer (). A detection circuit () detects the presence of the second variation on the basis of a second detection signal (D) received from the transducer (). The idea of the invention is that the detection circuit () is capable of using the phase-locked loop () of the information recovering circuit () to detect the presence of the second variation. The invention can be implemented very easily in, for example, DVD players to detect the presence of an information carrier () with DVD+RW format or an information carrier () with DVD−RW format. Only switching means () and some minor electronics have to be added; there is no need for an additional phase-locked loop.