positioning projections 7 b are provided in a leftwardly and rightwardly spaced relationship from each other at positions of the base portion 7 rather near to an upper end of a rear face 7 a as seen in fig3 the positioning projections 7 b serve as positioning elements for positioning an antenna hereinafter described each of the brackets 6 is integrally made of a metal material and includes a base portion 6 a elongated in one direction and a pair of attached portions 6 b projecting laterally from the base portion 6 a and formed integrally with the base portion 6 a as seen in fig2 each of the brackets 6 is attached at the base portion 6 a thereof to one of the peripheral edge portions 8 positioned on the left and right of the base portion 7 by means of a screw or the like and is attached at the attached portions 6 b thereof to a predetermined position of the housing 2 by means of screws or the like a drive circuit board 9 is attached at a rather downwardly displaced position on the rear face 7 a of the base portion 7 of the attachment base 5 as seen in fig3 and 4 the drive circuit board 9 is provided for driving the display block 3 and required electronic parts are mounted on the drive circuit board 9 the drive circuit board 9 is connected to the display block 3 by three wiring boards 10 in.