According to T 52/82 (OJ 1983, 416), an amended claim does not contain subject-matter which extends beyond the content of the application as filed if the preamble to the claim has been amended by substituting an appropriate more general term, which is apt to define a feature common to both the closest prior art described in the application as filed and the invention which is the subject of the application, for a specific term which is not apt to define that feature of the prior art (see also T 285/07).