Abstract: An electronic whiteboard system and assembly with optical detection elements is disclosed. The electronic whiteboard system includes a writing/display surface and a retroreflective perimeter surrounding the edge of the surface. A user can mark upon the surface or interact with an image displayed on the surface using an input device. The perimeter can reflect light beams emitted from optical detection elements located at the corners of the surface to identify the position of the input device relative to the writing surface and/or projected image. The electronic whiteboard assembly includes one or more electronic whiteboard systems coupled together with a connector element having two retroreflective surfaces.