What are the important changes impacting machine control systems?

The obligations on machine control system designers are more explicitly and in some cases more stringently defined. Consider the following:
"Control systems must be designed and constructed in such a way as to prevent hazardous situations from arising. Above all, they must be designed and constructed in such a way that:

• they can withstand the intended operating stresses and external influences
• a fault in the hardware or software of the control system does not lead to hazardous situations
• errors in the control system logic do not lead to hazardous situations
• reasonably foreseeable human error during operation does not lead to hazardous situations."

These requirements restate with clarity that a failure of or any other cause in a machine control system should not lead to a hazardous situation. The new wording reflects the state of the art in control system technology, where there is a distinction between software and hardware.