Abstract: An endless track for use in propelling a snowmobile. The endless track extends between a first lateral side and a second lateral side and includes an inner drive surface and an outer ground-engaging surface. The inner drive surface includes a plurality of longitudinally spaced inner drive lugs used to drive and rotate the endless track. The outer ground-engaging surface includes a plurality of treads, where each tread extends continuous and uninterrupted along a constant height from the first lateral side to the second lateral side a full width of the endless track.

Abstract: A modulated light beam obstacle detector for use as a safety mechanism in an automatic closure operator which must operate in varying ambient light conditions. If the obstacle detector senses the interruption of the light beam, the motion of the door is arrested or reversed. The obstacle detector uses an auxiliary light source connected in a feedback circuit to maintain a constant background illumination on the light detector and thereby hold the light detector in conduction at all times. In this manner, the presence of the light beam can be sensed regardless of the ambient light conditions.

Abstract: Disclosed is an image detection system having a photodetector, e.g. a photovoltaic cell, a photoconductor sheet, and a means, e.g., a liquid crystal light valve or an electrochromic light valve, matrix light valve having a plurality of individually addressable light valve cells. The image detection system also has means to identify the signal generated by the photodetector with the individual light cell switched to a light transmissive mode. Also disclosed is a method of detecting and updating an image using the image detection system.