The Review Guide requires that technical features with limited functions should be avoided as much as possible, because technical features with limited functions are different from upper-level concept generalization, whole-class product or machinery generalization, etc. The conceptual extension of the latter is relatively closed and stable, while the conceptual extension of technical features with limited functions can be extended, and the method of realizing a certain function is not immutable. With the passage of time and the development of technology, in the examination stage, there may be new implementations unknown to technicians or even inventors at any time, and these later new implementations with certain functions or effects obviously should not be included in the scope of patent protection.
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