This part of ISO 10924 defines terms and specifies general test requirements for circuit breakers for use in road vehicles with a nominal voltage of 12 V d.c., 24 V d.c, 48 V d.c. and 450 V d.c.This part of ISO 10924 is intended to be used in conjunction with other parts of ISO 10924. The numbering of its clauses corresponds to that of this part of ISO 10924 whose requirements are applicable, except where modified by requirements particular to this part of ISO 10924.This part of ISO 10924 is not applicable to circuit breaker holders (electrical centres or fuse-holders) used in vehicles.