Siemens simatic s5 Handbuch Seite 6

It is beyond the manufacturer's capabilities to have all these so-called SIMATIC-
compatible modules checked for their effect on our SlMATlC products. If the use of
so-called SIMATIC-compatible modules leads to defects in a SIMATIC automation
System, no warranty for such Systems will be given by Siemens.
In the event of product liability damages due to the use of so-called SIMATIC-
compatible modules, Siemens are not liable since we took timely action in warning
Users of the potential hazards involved in so-called SIMATIC-compatible modules."