Abstract: Equipment for lighting a work area has a plurality of light sources, at least one of which is usually lighted; the others are spare light sources and are usually turned off. The equipment has means such as an optical fiber to conduct light from the light source to the work area. Converting means is provided with the equipment to distribute electric power selectively to the light sources. Detecting means is also installed in the equipment to detect cutting off of the light source which is in the lighted condition. The converting means changes the distribution of the output from the power supply to a light source other than the light source which was cut off.

Abstract: The start of the final tightening of a screwdriver and rotation of the screwdriver after the start of the final tightening are detected. The detected rotation is compared with a standard value. The screwdriver should rotate very little during the final tightening, if it is normally operated. Consequently when the detected rotation is more than the standard value, one may assume false rotation of the screwdriver has occurred.