Abstract: An articulated optical arm adapted to optically link an endoscopic telescope to a viewing station through a series of mechanically interhinged and optically intercoupled arm sections, the last arm in the series being coupled to a terminal eyepiece through an image-erecting barrel which is rotatable by a barrel rotator to correct for image displacement. Associated with the endoscope are surgical instruments for performing an operation at the surgical site viewed by the endoscope. In order to make it possible for a surgeon while manipulating the instrument with his hands to rotate the barrel to maintain an erect image, the barrel rotator includes a bi-directional motor controlled by a foot-operated switch.