Abstract: In a disc reproduction apparatus 1 for reproducing information signals from a disc recording medium whereon a first synchronization pattern is formed on a recording track in predetermined cycles and more than one second synchronization pattern with fewer bits than the first synchronization pattern which has been recorded between first synchronization patterns adjacent to each other, second synchronization patterns are detected without fail and highly accurately. The timing of a second synchronization pattern detecting means 7 for fetching the reproduction signal R is made variable through making the window width of window signal WIN variable based on the results (F1 and F2) of the detection of first and second synchronization patterns by first and second synchronization pattern detecting means 6 and 7.

Abstract: An improved apparatus for detecting address information recorded on a recording medium such as an optical-magnetic disc is disclosed. The header information is recorded on each sector of the disc recording medium and is constituted by a sector mark indicating a head position of the corresponding sector, a plurality of address marks, and subsequent address information data. In a first preferred embodiment, a number of bytes starting from an end position of the address information and ending at a head position of the address information is counted and an address information recognition circuit is provided so as to provide an address information recognition start signal for the address information recognition signal at a predicted position of the head position.

Abstract: A disc recording and/or reproducing apparatus for recording and/or reproducing information signals on or from an optical disc on which there is formed a spirally extending recording track is disclosed. The apparatus includes fundamental clock generating circuits for generating fundamental clocks CK.sub.A and CK.sub.B having different frequencies associated with recording regions E.sub.A and E.sub.B of different recording densities formed on the optical disc, and a clock changeover circuit for making a changeover between the fundamental clocks CK.sub.A and CK.sub.B from the fundamental clock generating circuits based on the boundary position information between the recording regions E.sub.A and E.sub.B.

Abstract: An improved apparatus for detecting address information recorded on a recording medium such as an optical-magnetic disc is disclosed. The header information is recorded on each sector of the disc recording medium and Is constituted by a sector mark indicating a head position of the corresponding sector, a plurality of address marks, and subsequent address information data. In a first preferred embodiment, a number of bytes starting from an end position of the address information and ending at a head position of the address information is counted and an address information recognition circuit is provided so as to provide an address information recognition start signal for the address information recognition signal at a predicted position of the head position.