Abstract: An improved electrode operating mechanism for control of the discharge of carbon arc lamps for light fastness testing devices. Vertically spaced upper and lower electrode holders have a plurality of electrodes opposed to each other. Two vertical supports extend between upper and lower bases, the vertical supports each having a pair of spaced parallel guide rails extending therealong, each holder having laterally projecting arm members extending from the opposite ends thereof and between the rails. A cylindrical slide member is mounted on the end of each arm member and is slidably engaged in linear sliding contact with the surface of the parallel rails on the sides thereof away from the holders. First wires are attached to the cylindrical slide members on the lower electrode holders and extend upwardly through the upper base through axial bores in the upper cylindrical slide member, and two second wires attached to the upper holders extend upwardly through the upper base.

Abstract: A support includes a support element having two electrode contact areas for each electrode to be clamped. Each contact area has fixed thereto a conductive carbon plate. A clamping device has a non-conductive clamping surface for clamping each electrode against its respective pair of carbon plates.