When interpreting a patent claim, it must be taken into account that a patent's doctrine seeks to distinguish itself from the state of the art described in it. If the specification equates to known prior art with the claim's preamble, the features of the characterising portion of the patent shall – in case of doubt – not be regarded as being understood according to features which are found in the state of the art from which they currently should have been distinguished. (Guiding principle of the Court)
