Safety switch S1: According to BIA report 2/2008, error exclusion to up 100000 cycles is possible, providedthe manufacturer has confirmed this. If no confirmation exists, S1 is included in the calculation as follows.Relays K1 and K2 are both connected to the safety function. The non-functioning of a relay does not lead toa dangerous situation, but it is discovered by the feedback. Furthermore, the B10d values for K1 and K2 areidentical.There is a coupling coefficient between the components that are connected via two channels. Examples aretemperature, EMC, voltage peaks or signals between these components. This is assumed to be the worstcase estimation, where β =10%. EN 62061 contains a table with which this β-factor can be preciselydetermined. Further, it is assumed that all usual measures have been taken to prevent both channels failingunsafely at the same time due to an error (e.g. overcurrent through relay contacts, overtemperature in thecontrol cabinet).It follows for the calculation of the PFHD value for safety function 1: