According to an embodiment of the present invention a projection facility for projecting image contents onto an inside wall in an open cabin of a transport means, with which any given image contents can be projected onto a curved inside wall in a large-scale manner. Conductive via-holes extend between two non-adjacent conductive layers for transmitting high-frequency signals therebetween. A second magnetic core is located inside the slotted air gap between opposing inner walls of the slotted air gap. The current mirror unit is coupled between the first current source and the second current source. The result is a clean slide-step portamento curve. The cable reel may be rotatable with the base or rotatable independent thereof.