A developer unit for an image forming apparatus is provided. The x-ray diffraction patterns of the crystals provided by the present invention are of sufficiently high resolution for determining the three-dimensional structure of ribosomes and ribosomal subunits, for identifying ligand binding sites on ribosomes and ribosomal subunits, and for molecular modeling of ligands which interact with ribosomes and ribosomal subunits. The access network transmits one or more forward traffic channels at the fixed rate according to the received identification information. Two electric contact terminals are electrically connected to the two spring means respectively.