ANSI INCITS-328-2000 pdf download Information Technology – 19 mm DD-2 Helical Scan Digital Computer Tape Cassette for Information Interchange
1.2 Purpose
The purpose of this standard is to ensure a direct and unique correspondence between user data and the format recorded on tape. In order to ensure data interchange using this standard, it is nec- essary for interchange parties to agree upon performance levels and source data format. This stan- dard is distinct from a specification in that it delineates a minimum of restrictions consistent with compatibility in media interchange transactions.
The performance levels contained in this standard represent the minimum acceptable levels of performance for interchange purposes. They, therefore, represent the performance levels that the interchange items should meet or surpass during their useful life and, thus, define end-of-life cri- teria for interchange purposes. The performance levels in this standard are not to be employed as substitutes for purchase specifications.
Wherever feasible, quantitative performance levels that shall be met or exceeded to comply with this standard are given. In all cases, including those in which quantitative limits for requirements falling within the scope of this standard are not stated but left to agreement between interchange parties, standard test methods and measurement procedures shall be used to determine such limits. Except as indicated above, the interchange parties complying with the applicable standards should be able to achieve compatibility without the need for additional exchange of technical informa- tion.
1.3 Application
1.3.1 Conformance A data storage cassette complies with this standard if it satisfies all the mandatory requirements contained herein. The tape requirements shall be satisfied throughout the length of the tape.
1.3.2 Dimensions The original dimensions and quantities for all numeric values in this standard are in the Interna- tional system of units (SI). Conversions of these units to the U.S. customary engineering units (similar to the British Imperial units) and centimeter-gram-second electromagnetic units (cgs- emu) have been incorporated in accordance with the procedures described in ANSI/IEEE 268, American National Standard metric practice. Units of either of the two measurement systems may be referred to but the two systems should not be intermixed or reconverted. Conversions of tolerance dimensions and quantities in this standard have been performed in accordance with method A of ANSI/IEEE 268 and ISO 370, International Standard Tolerance Dimensions – Con- versions from Inches to Millimeters and Vice Versa, to maintain the implied correspondence between the accuracy of the original data and the number of significant digits and rounding of the converted values. In the national standards of ISO member bodies, additional rounding may be done to produce “preferred” values. These values should lie within or close to the original toler- ances.