Abstract: A computer device 1 for production equipment comprises an arithmetic unit 10, an input device 11 for inputting operation data, a display device 12 for displaying operation data, and an HDD device 13 for storing an arithmetic unit 10 executed processing program, and operation results. In the HDD device 13, there are provided a main drive unit and a backup drive unit, which are constituted so as to maintain the same contents, and to selectively connect the arithmetic unit 10 to one of the drive units inside the HDD device 13, a drive unit selecting circuit 2 is provided on the HDD device 13 side, and a switch for switching this drive unit selecting circuit 2 is provided on the outside of the computer device 1.

Abstract: A sub control panel for use in maintenance work has a control switch, enable switches and manipulation prohibition members. The sub control panel is configured such that the control switch is not activated unless the enable switches are being kept ON by one hand of the operator and the operator is prevented by the manipulation prohibition members from manipulating with the one hand from turning ON the enable switches. When the sub control panel is to be used, the operator must use both hands and is hindered from inserting both hands to a driven part of a machine to be subjected to maintenance work when the machine is operating.

Abstract: A photoelectric position encoder using diffraction imagery has a laser light source emitting parallel, coherent light. As least one light sensing device senses the light amount received from the light source and provides an output signal corresponding thereto. A transfer slit plate having periodic slits is disposed between the light source and the light sensing device. The light sensing device thus senses the variation in the received light amount caused by the movement of the transfer slit plate. The light sensing device also senses brightness and darkness fringes of a diffraction image caused by the periodic slits of the transfer plate. Circuitry is coupled to the light sensing device and issues a position signal corresponding to the position of the transfer slit plate.