Abstract: Photoelectric sensing apparatus is operative for sensing the absence of filament at a particular point on a supply bobbin wherein several strands of filament will still be present on the bobbin. The sensing apparatus includes a light source which directs an angled photoelectric beam at a sensing point near the center of the bobbin and a light sensor which detects reverse reflections of the beam. If there is filament present at the sensing point, the beam will reversely defect off the round surface of the filament back to the light sensor. If there is no filament present at the sensing point, the beam deflects off the exposed core of the bobbin away from the light sensor in a different direction. Electronics means are provided which cooperate with the sensing apparatus to automatically shut-down the machine pursuant to absence of filament at said sensing point.