Embodiments of an Ethernet transceiver are disclosed. Viewport parameters that specify geographic locations and zoom levels for several viewports are received, and respective viewport indicators for these viewports are displayed. The first of the polarization states is directed to a first birefringent optical waveguide having a first chirped grating having a first reference reflection point. In another arrangement the coupling includes a double constant velocity joint in which the control mechanism is located in a control tube connecting the two joints. The outlet from the second valve can be drained out, and that respective actuateable valves can be actuated by signal from predetermined sensor or sensors.