A drive line apparatus has a pair of tubular shafts configured to fit telescopically. The chambers of the second set of fluid chambers are interleaved with the chambers of the first set of fluid chambers. The time interpolator has flip-flops connected in parallel for receiving output data from an LSI under test, a delay circuit for successively inputting strobes delayed at a constant timing interval to the flip-flops and outputting time-series level data, and an encoder for receiving the time-series level data from the flip-flops and encoding it into position data indicating an edge timing. The wedged implant can be interposed between adjacent vertebrae that form part of an abnormal spinal curvature, thereby realigning the vertebrae and restoring the normal curvature to the spine.