A wireless communication system and in particular to a wireless communication system for digital audio players that provides for increased functionality, such as communication, interaction and synchronization between a computing platform and various mobile, portable or fixed digital audio players, as well as providing a communication link between the various digital audio players themselves. The hub adaptor comprises a single piece body having an outwardly extending mounting flange with a first plurality of apertures that define a wheel rim attachment interface. The configuration of the tubular rails substantially prevents use of the swimming machine as a ladder. The sheared products computed from heterodyne measurements at the receivers in the array based on the reflected signals from the three transmitters are used to determine and correct for the combined transmitterreceiver phase errors at each of the receivers in the array. Artemisia capillaris is about 5 to about 21 weight % of the liquid preparation, Plumeria acutifolia is about 65 to about 90 weight % of the liquid preparation, and Melaleuca alternifolia is about 4 to about 16 weight % of the liquid preparation respectively. Each light directing portion also includes a first base that is defined by the plurality of first side facets and has a first minimum dimension.