A bidirectional digital data communication system which generate phase coherent upstream clock and carrier signals from recovered downstream clock generated from a master clock in a central unit. A planar substrate is provided with channel-shaped structures and the channel-shaped structures are filled with a wave guide material. The stator comprises a stator core including a plurality of stator teeth that are circumferentially arranged around a common axis. Stations in a group can schedule a group address frame to be sent during the CBP and group SP of a specific periodic BI. A small volume of the warmed alcohol fuel is maintained in the fuel injectors. A tower section is disclosed for connecting adjacent tower sections, each comprising a tower section shell, a tower section flange, and a radius transition over a transition zone between the shell and flange, wherein the tower section connecting arrangement comprises at least one flange assistant and a number of fasteners to connect together the flanges and the flange assistants.