Fuses for use by authorized persons are generally designed to be used in installations where the fuse-links are accessible to, and may be replaced by, authorized persons only. Fuses for use by authorized persons according to the following fuse systems also comply with the requirements of the corresponding subclauses of IEC 60269-1, unless otherwise defined in this standard. This standard is divided into fuse systems, each dealing with a specific example of standardized fuses for use by authorized persons: Fuse system A: Fuses with fuse-links with blade contacts (NH fuse system) Fuse system B: Fuses with striker fuse-links with blade contacts (NH fuse system) Fuse system C: Fuse-rails (NH fuse system) Fuse system D: Fuse-bases for busbar mounting (NH fuse system) Fuse system E: Fuses with fuse-links for bolted connections (BS bolted fuse system) Fuse system F: Fuses with fuse-links having cylindrical contact caps (NF cylindrical fuse system) Fuse system G: Fuses with fuse-links with offset blade contacts (BS clip-in fuse system) Fuse system H: Fuses with fuse-links having "gD" and "gN" characteristic (class J and class L time delay and non time delay fuse types) Fuse system I: gU fuse-links with wedge tightening contacts Fuse system J: Fuses with fuse-links having "gD class CC" and "gN class CC" characteristics (class CC time delay and non-time delay fuse types) Fuse system K: gK fuse-links with blade for bolted connections – High fuse-link ratings from 1 250 A up to 4 800 A (master fuse-links) NOTE The above-mentioned fuse systems are standardized systems in respect to their safety aspects. The National Committees can select from the examples of standardized fuses one or more systems for their own standards