A level comprises a frame defining first and second parallel channels and first and second rails fitted slidingly in the first and second channels respectively. The functional tip may comprise at least one active electrode for creating the perforation through the application of Radio Frequency energy. Once the execution agent deposits the collected artifacts in the specified location in the repository, a summary of collected artifacts is propagated to the controller. And control a rate of variation in the rotation speed of the engine to be smaller, when the rotation speed of the power generating motor increases than when the rotation speed of the power generating motor decreases toward zero as a result of controlling the engine based on the target engine power.