A transducer is moved in a seek operation from an initial track to a target track on a disk based on a current command. Some embodiments cache timing-related information associated with a source driver that drives an input of a sequential cell that is being sized, andor timing-related information for each output of the sequential cell that is being sized. The command controller has a first wireless interface for transmitting the command signal on a first wireless network. A vehicle may have a differential mechanism, which combines rotation powers on input side and output side of the hydraulic transmission.