Patent ID: 8302857

Claim:
A tamper detection mechanism for detecting tampering when a sub system is removed from a host device, comprising: a screw member comprising a head portion, a major diameter shaft portion and a minor diameter shaft portion and which a thread portion formed on said minor diameter shaft portion is screwed into a screw hole in said host device to fix said sub system to said host device; a through hole which is provided in said sub system and through which said major diameter shaft portion passes; a lever member which withdraws from said through hole as the lever member is pushed by said major diameter shaft portion when said screw member is tightly screwed, and advances into said through hole when said screw member is loosened; and a detection switch which detects a tightly screwed condition or a loosened condition of said screw member based on the withdrawal or advancement of said lever member; wherein when said screw member is loosened, the lever member advances into a space of said through hole which is formed by a diameter difference in a radial direction between the minor diameter shaft portion and the major diameter shaft portion and thereby the loosened condition of said screw member is detected by the detection switch.