To simply and reliably differentiate sorts of strobe units.

The circuit pattern face of the printed circuit board 30 of each strobe unit 13 has been coated with a red resist layer 37 whose color is predetermined to every sort of strobe units. Forty nine strobe units 13 are arranged in the same direction and contained in a strobe tray 38. When a strobe unit 39 different in sort from the strobe units 13 is included, since the resist layer of the strobe unit 39 is not red, but, e.g., green, the strobe unit 39 can be differentiated in a moment of time even if the strobe unit 39 closely resembles the strobe units 13 in appearance, e.g., the strobe unit 39 has the same flashing part as the strobe units 13.