Patent ID: 7319597

Claim:
A subrack, comprising: a plurality of plug-in units, each comprising a printed circuit board and a mounting panel attached to an end of the printed circuit board, each of opposite ends of the mounting panel comprising an alignment pin, and a particular combination of code pins; a pair of parallel sidewalls; and a bottom wall and a top wall fixed between the side walls to cooperatively define a receiving space therebetween adapted to accommodate the plug-in units; wherein each of the bottom wall and top wall comprises: a first plate comprising a main portion and a recessed edge portion, the main portion defining a plurality of spaced slide channels for slidably receiving the printed circuit boards therein respectively, and a plurality of alignment holes adjacent corresponding slide channels for receiving the corresponding alignment pins to guide the plug-in units into the receiving space, the recessed edge portion forming a plurality of L-shaped flakes substantially in front of the slide channels respectively; and a second plate engaging with the first plate; wherein any one or more of a height, a length, and a deviation relative to the corresponding slide channel of each of the flakes varies relative to another one of the flakes according to different combinations of corresponding code pins on the corresponding mounting panels, in order that the flakes respectively match the combinations of the corresponding code pins on the corresponding mounting panels and thereby prevent improper insertion of the corresponding plug-in units into the subrack.