Tiêu chuẩn quốc tế

• Số hiệu / Standard Number: ANSI/INCITS 48:1986
• Năm ban hành / Publication date: 1986
• Tình trạng / Status: A - Còn hiệu lực
• Tên tiếng Anh / Title in English: Information Systems - Magnetic Tape Cassettes for Information Interchange - 3 - 81 -mm (0 - 150-in) Tape at 32 bpmm (800 bpi), Phase Encoded
• Số trang / Page: 31

Phạm vi áp dụng / Scope of standard

This American National Standard for unrecorded and recorded cassettes containing 3.8 1 -mm (O.l.SO-in) -wide magnetic tape presents the minimum requirements for mechanical and magnetic interchangeability of the cassette and for data interchange between information processing systems, which are capable of utilizing a standard code for information interchange as agreed upon by the interchange parties, using a data density of 32 bpmm (800 bpi). NOTE: Conversion of 800 bpi to SI units results in 31.5 bpmm. For the sake of simplicity, the data density is stated as 32 bpmm (800 bpi) nominal in this standard.

The cassette is of the twin hub-coplanar type, loaded with 3.81-mm (0.150-in) -wide magnetic tape.

This standard applies to cassettes and data used for interchange. Where it applies to cassette testing only, this is specifically stated.

Data labeling and file structure should conform to American National Standard for Information Processing - Magnetic Tape Cassette and Cartridge Labelling and File Structure for Information Interchange, ANSI/IS0 4341-1978.

CAUTION: The user's attention is called to the possibility that compliance with this standard may require use of an invention covered by patent rights. By publication of this standard, no representation of warranty is made or implied that there is no license that may be required to avoid infringement in the use of this standard.

Purpose

This standard defines the requirements and supporting test methods necessary to ensure data interchange at acceptable performance levels. It is distinct from a specification in that it defines a minimum number of restrictions consistent with compatibility in interchange transactions.

The performance levels contained in this standard represent the minimum acceptable levels for interchange purposes that the interchanged items should meet or surpass during their useful life, and thus define end-of-life criteria. They are not intended to be employed as substitutes for purchase specifications.

Wherever feasible, quantitative performance levels that shall be met or exceeded in order to comply with this standard are given. Quantitative limits for some of the requirements falling within the scope of this standard may not be stated but are left to agreement between interchange parties. Standard test method and measurement procedures shall be used to establish such quantities.

The original dimensions and quantities for all numeric values in this standard are in the International System of Units (SI). Conversions of these units to U.S. Customary engineering units (similar to British Imperial units) and centimeter-gram-second electromagnetic units (cgs-emu) have been incorporated in accordance with the procedures described in American National Standard Metric Practice, ANSI/IEEE 268-1982. Units of either of the two measurement systems may be referred to, but the two systems should not be intermixed or reconverted.'Conversions of toleranced dimensions and quantities in this standard have been performed in accordance with either Method A or Method B of ANSI/ IEEE 268-1982 and Toleranced Dimension - Conversion from Inches into Millimeters and Vice Versa, IS0 370-1975 as required to maintain the implied correspondence between the accuracy of the original data and the number of significant digits and rounding of the converted values. Units of either of the two measurement systems may be referred to, but the two systems should not be intermixed or reconverted. Method A should be used to achieve economy unless a requirement for absolute assurance of fit justifies use of Method B. Conversions made in accordance with Method B are so indicated. In the national standards of IS0 member bodies, additional rounding may be done to produce "preferred" values. These values should lie within or close to the original tolerance.

NOTE: t (the dagger symbol) appearing next to U.S. engineering units indicates that the value was rounded to a preferred value.

Except as indicated in 1.2.3, interchange parties complying with the applicable standards should be able to achieve compatibility without need for additional exchange of technical information.