Abstract: Disk apparatus for detecting address marks in the data of a zoned constant angular velocity (ZCAV) recording disk. The apparatus includes a detecting unit for detecting sector marks in the data. Time delay circuitry establishes a time delay between sector mark detection and an address mark detecting gate period. A portion of the time delay is established by a pulse count which is independent of the reproducing frequency corresponding to the zone of the sector mark. A second portion of the time delay is established responsive to the recording frequency. The time delay so established is used to position the address mark detecting period to reliably detect the address mark.

Abstract: Rubber-modified styrene resins with excellent impact resistance are prepared by formulating a feed from a styrene-based monomer, or a mixture thereof with comonomers and high-viscosity rubber, an organic peroxide, and, if necessary, all inert organic solvent, preheating and continuously supplying the feed to one end of a plug flow type reactor equipped with an agitator, performing the preliminary polymerization to a conversion sufficiently high for the transformation of the rubber in the feed into particles while controlling the weight average particle diameter of the rubber particles to 0.8 to 5 .mu.m, withdrawing the prepolymerized feed from the other end of the reactor, and supplying it to a following plug flow type reactor for continuous enhancement of tile conversion.