This part of ISO 10972 establishes requirements which apply specifically to the mechanisms and related components of tower cranes, in addition to the general requirements given in ISO 10972-1. These additional requirements concern a) the arrangement, features and characteristics of the crane mechanisms, and b) the minimum requirements for certain mechanism components. Rules for the proof of competence calculation regarding different limit states (yield strength, fatigue, wear) are excluded from this part of ISO 10972. This part of ISO 10972 is not applicable to the climbing mechanisms and related components used on tower cranes, nor to the climbing frame.