Rule 43(2) defines in sub-paragraphs (a), (b) and (c) the situations where, without prejudice to the requirements of Art. 82, an application is allowed to comprise a plurality of independent claims in the same category (see F‑IV, 3.2 and 3.3). The express reference to Art. 82 in Rule 43(2) makes clear that the requirement for unity of invention must still be met. Where the application both lacks unity of invention and fails to comply with the requirements of Rule 43(2), it is at the discretion of the division to raise an objection under Rule 43(2) or Art. 82, or both.
A plurality of inventions in the same category may constitute a group of inventions so linked as to form a single general inventive concept. Examples of inventions in the same category are alternative forms of an invention or interrelated inventions.
Alternative forms of an invention may be claimed either in a plurality of independent claims or in a single independent claim (see also F‑IV, 3.7). In the latter case, the presence of the two alternatives as independent forms may not be immediately apparent. In either case, the same criteria are applied in deciding whether or not there is unity of invention, and lack of unity of invention may therefore also exist within a single claim.
Several independent claims in the same category directed to interrelated subject-matter may meet the requirement of unity even if it appears that the claimed subject-matter is quite different, provided that technical features making a contribution over the prior art at hand are the same or corresponding. Examples of such situations include a transmitter and the corresponding receiver or a plug and the corresponding socket (see also F‑IV, 3.2).
Thus, special technical features relating to the single general inventive concept must be either implicitly or explicitly present in each of the independent claims.