Where safety is based on the proper operation of the machine control system, it shall be designed so that to ensure a minimal probability of functional errors. Otherwise, any errors shall not lead to the loss of the safety function.
In Europe, to meet these requirements it is highly recommended to use the harmonized standards developed by mandate of the European Commission (assumption of conformity).
In the event of an accident, using the harmonized standards saves extra time and costs where proof of conformity of the safety-related control system to the essential requirements of the Machinery Directive shall be demonstrated.
Given hereunder are the basic concepts of the new standards ISO 13849-1 and IEC 62061 which supersede EN954-1 as regulatory instruments covering machine control systems.