Overview
ISO 1681:1973 - Information processing - Unpunched paper cards - Specification defines the physical and material characteristics of general‑purpose unpunched paper cards intended for information interchange between different punched‑card devices. The standard specifies dimensions, paper properties, mechanical and electrical characteristics, test methods and conditioning/storage guidance to ensure reliable feeding, reading and handling across equipment.
Key topics and requirements
- Card dimensions and geometry
- Nominal size: 187.32 × 82.55 mm (7.375 × 3.250 in). Actual‑tolerance parallelograms and corner geometry (including a diagonally cut corner and optional rounded corners) are defined to control squareness and edge straightness.
- Paper and sheet properties
- Substance: 161 g/m² ±5%.
- Thickness: 0.178 ±0.01 mm.
- Paper must be 100% chemical pulp (no groundwood).
- Ash content ≤ 2%; pH (hot extraction) not below 5.0.
- Mechanical strength and durability
- Minimum bursting strength as specified in the standard (see ISO 2758 method).
- Internal tearing resistance and folding endurance requirements (including retention after accelerated ageing).
- Limits on maximum curl (different limits parallel, perpendicular and diagonal to grain).
- Surface and handling characteristics
- Static coefficient of friction 0.30–0.45; kinetic ≥ 75% of static.
- Maximum abrasion loss 50 mg per side.
- Smoothness / roughness limits and printability requirements (non‑abrasive, non‑conductive inks).
- Electrical and dimensional stability
- Electrical resistance between 40 and 200 MΩ under defined conditions and apparatus.
- Maximum expansion/contraction on humidity change: machine direction 0.25%, cross direction 0.70% (20% ↔ 75% RH).
- Testing & conditioning
- Conditioning and tests performed at standard atmospheres (typically 23 °C, 50% RH) with referenced ISO methods for thickness, substance, tearing, stiffness, roughness, bursting and abrasion.
Applications and users
- Manufacturers of punched‑card stock and paper suppliers ensuring compatibility with legacy and specialized card readers.
- Designers, maintainers and integrators of punched‑card equipment in industrial, archival, museum or legacy data‑processing environments.
- Quality, procurement and compliance teams specifying card material and test acceptance criteria for interchangeability.
- Conservation professionals and institutions preserving historical data on card formats.
Related standards
Referenced test and method standards include: ISO/R 534, ISO/R 536, ISO/R 1974, ISO/R 2144, ISO 2493, ISO 2494, ISO 2758 (see ISO 1681 for full references and test procedures).
Keywords: ISO 1681:1973, unpunched paper cards, punched card devices, card dimensions, paper requirements, friction coefficient, electrical resistance, information processing, card storage humidity.
