A DC converter comprises a single primary circuit which is coupled to each of a plurality of output circuits in respective time periods, the coupling being provided by switching in the output circuits. The aforementioned magnet for magnetic bias is a bonded magnet containing a resin and a magnet powder dispersed in the resin and having a resistivity of 1 \u03a9\xb7cm or more. The indicator receiving portion has a wall structure extending at an angle from the generally planar portion adjacent to an aperture established through the mirror back plate. The swirling directions of the medium in different sprays are opposite to each other, whereby a preferably homogeneous mist spray spread over a large area is achieved. When the main relay opens, the auxiliary contact is maintained closed during a given time interval due to the magnetic flux generated by the low resistance coil.