Specifies the physical and magnetic characteristics of magnetic tape cassettes, using magnetic tape 12, 65 mm wide so as to provide physical interchange of such cassettes between drives. Also specifies the quality of the recorded signals, the recording method and the recorded format, called Digital Tape Format-1 (DTF-1), thereby allowing data interchange between drives by means of such cassettes. The format supports variable length Logical Records, high speed search, and the use of a registered algorithm for data compression. This International Standard specifies two sizes of cassette.