A connector assembly arrangement comprising, disposed on the faces of a circuit board in an electronic device, connector assemblies which, along with having a plug connector that incorporates a photoelectric conversion element capable of converting optical signals and electrical signals from one to the other and a receptacle connector with which said plug connector is mated, have the plug connector and the receptacle connector electrically connected through mutual contact between terminals; wherein the plug connector, from which a fiber optic cable for optical signal transmission that is connected to the photoelectric conversion element extends in one direction from said plug connector, also has terminals connected to the above-mentioned photoelectric conversion element; the fiber optic cable is a single fiber optic cable; and a plurality of connector assemblies are disposed on at least one of the two faces of the circuit board.