An image forming apparatus having a print head that reciprocates along a guide rail includes a carriage on which the print head is mounted. A system and method of the present invention may be used to track the location of objects which are coupled to coded information devices. One or more ported seals are positioned within the housing and adjacent the cylinder to minimize leakage. Three of the six terminals, non-adjacent and alternatingly located in the direction of rotation, are electrically connected directly with mid-terminals facing in radial opposition. The self-illumination unit is disposed over the filter layer, including a light-transmissible electrode, a light emitting layer, and a black electrode. When coupling a pair of square bars, the first and second square bars provided respectively with first and second anti-release grooves are arranged to abut each other rectangularly and the first and second engagement sections of the inner joint are loosely put into the first and second anti-release grooves respectively.