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, published in 2006, and IEC 62061, published in 2005, which supersede the international Standard ISO 13849-1:1999 and the equivalent European Standard EN954-1 (whose validity has been extended, only in Europe, until 31st December 2011) as regulatory instruments covering machine control systems.