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Guidelines for Examination


10.2 Unexpected technical effect; bonus effect

An unexpected technical effect may be regarded as an indication of inventive step. It must, however, derive from the subject-matter as claimed, not merely from some additional features which are mentioned only in the description. However, if, having regard to the state of the art, it would already have been obvious for a skilled person to arrive at something falling within the terms of a claim, for example due to a lack of alternatives thereby creating a "one-way street" situation, the unexpected effect is merely a bonus effect which does not confer inventiveness on the claimed subject-matter (see T 231/97 and T 192/82).