Provided are intermediate coupling unit that can maintain universal applicability of image forming apparatus so it can singly form imagesbe installed in small offices, but can also couple two apparatuses if necessary, and image forming apparatus adaptable to this unit. A predetermined voltage obtained by adding the second voltage to a threshold voltage of a transistor in the secondthird switch circuit is applied to the gate terminal thereof, and ends of the data lines are connected to the source and drain terminals thereof. In some embodiments, the housing includes a fastening system for securing and electrically grounding internal components to the housing.