不可拆线的盒式保险丝。尺寸、与额定电流有关的额定电压、分断能力试验。两个等级的熔断器，以两倍或三倍额定电流熔断。交叉参考:BS 381CBS 646取代了BS 646:1958中B型熔断器的要求。

Non-rewireable cartridge fuse-links. Dimensions, rated voltage related to rated current, breaking-capacity test. Fuse-links of two grades, which blow at two or three times their rated currents.Cross References:BS 381CBS 646Replaces the requirements for type B fuse-links in BS 646:1958.