This part of IEC 61834 specifies the content, format and recording method of the data blocks forming the helical records on the tape. It describes the common specifications for cassettes, modulation method, magnetization and basic system data, for helical-scan digital video cassette recording system using 6,35 mm (1/4 inch) magnetic tape. The object of this standard is to define the electrical and mechanical characteristics of equipment which will provide for the interchangeability of recorded cassettes.