An oscillator circuit may selectively switch between a normal mode and a low-power mode in response to a mode signal. Air is capable of flow to the positive electrode. The present disclosure also relates to a crane for carrying out the method. The latch automatically moves from the first position to the second position to trap the rod between the latch and the ramp when the ramp is moved toward the rod and the latch contacts the rod, thereby attaching the ramp with respect to the load-bearing structure. The movable members can be moved out or in relative to the supporting member. The cam units are aligned on a common axis and each unit includes an in-line cam assembly that includes a rotary cam and two stationary cams, one above and one below the rotary cam.