PURPOSE: To facilitate assembling operation by fitting a printed board to a fitting member according to the fitting member and a printed board to a photoconductor, and positioning and mounting a panel plate which has a display window on the front surface side of a light reception type display element.

CONSTITUTION: The printed boards 3 and 6 are fitted according to the fitting member 1 which protects circuit components driving the light reception type display element 9 fitted on the reverse surface side of the printed board 3 and serves as a spacer for setting the height size of fitting in a housing 32. The photoconductor 10 equipped with the light reception type display element 9 which is connected electrically to the printed board 3 and 6 and has a display part is positioned and fitted to the 2nd printed board 6 by fitting a fitting pin 10f in a fitting hole 6a. Further, the panel plate 20 which has the display window 20a is mounted on the photoconductor 10 by engaging a positioning projection part 21 in a recessed groove and the display plate 24 is positioned and mounted on the panel plate 20 by engaging the positioning projection part 12 with the recessed groove. Consequently, the assembling operation is facilitated.