This International Standard defines the electrical and mechanical characteristics of equipment which permits the interchangeability of 12,65 mm cassettes containing digitally recorded composite video programmes. This standard specifies the content, format and recording method of the data blocks forming the helical records on the tape containing video, audio and associated data using the 12,65 mm (0,5 in) type D-3 cassettes. In addition, this standard specifies the content, format and recording method of the longitudinal record containing tracking information for the scanning head associated with the helical records, as well as the longitudinal cue audio and time and control code tracks. The requirements given relate to 525-line composite television signals with a frame frequency of 29,97 Hz nominal (hereinafter referred to as "525/60 system") and to 625-line composite television signals with a frame frequency of 25,00 Hz (hereinafter referred to as "625/50 system").