A water supply assembly for mounting on a vehicle rectangular roof is described. According to the invention, the connection ends of the electrodes of one electrode pair are located on opposite edges of the panel and the power circuit of each pair of adjacent electrodes forms a current loop that does not surround the metallic plate. In one embodiment, the at least one sensor element comprises an inner sensor, and a plurality of outer sensors surrounding the inner sensor. The present invention easily adjusts the angle of the display means so as to comply with a user’s wishes, and finely adjusts the angle of the display means by a small force. Furthermore, a multi-layer tag manufactured from said multi-layer material is provided.