In general, in one aspect, the invention features a circuit, method, and computer-readable media for calculating xmody, wherein x and y are binary numbers, and wherein y is an even number. The device selectively dispenses any of one or more fluids contained within the device. The wings each include a first wing element extending radially outward from a first attachment position on the wing support, a second wing element extending radially outward from a second attachment position on the wing support, and a third wing element connecting the first and second wing elements. A hard disk drive sequentially moves a head to an adjacent data track in a band and performs a head switch at the band end in its data accessing. Other embodiments are also described. If the mode is fixed mode, at least one activation signal is transmitted based on a fixed code transmission scheme and including the stored fixed code.