Rule 43(2) refers expressly to Art. 82. This makes clear that the requirement of unity has to be met by the subject-matter of the independent claims in the same category. Thus, special technical features relating to the single general inventive concept within the meaning of Rule 44 must be either implicitly or explicitly present in each of the independent claims.
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 the special technical features making a contribution over the prior art are the same or corresponding within the meaning of Rule 44. Examples of such situations include a transmitter claimed together with a corresponding receiver, a plug claimed with a corresponding socket, etc. (see also F‑IV, 3.2).
Special attention is required in the case of claims characterised by a combination of elements (e.g. A+B+C), accompanied by claims relating to sub-combinations (e.g. A+B, A+C, B+C or A, B, C separately). Even if the claimed sub-combinations define patentable subject-matter, and the combination claim includes all the features of the claimed sub-combinations, lack of unity of invention may still arise.
Where the application both lacks unity of invention and fails to comply with the requirements of Rule 43(2), the examiner may raise an objection under either Rule 43(2) or Art. 82 or under both. The applicant cannot contest which of these objections has priority (see T 1073/98, Reasons 7.2).