A lamp base may include a cylindrical body having an end surface, a first step portion and a second step portion, a first upper pin connector provided on the first step portion, a second upper pin connector provided on the second step portion, and a first and second lower pin connector provided on the end surface. In this state, a bit line switch circuit connects one of complementary bit lines to a first voltage node, and connects the other complementary bit line to a second voltage node in blocks on both sides. Each of the plurality of conductive members includes a conductive material formed integrally from the upper surface through the lower surface of the circuit board, and an insulating material covering an outer circumference of the conductive material. Then, the outer parity is scattered with respect to each of the sectors of the data block to be interleaved. The probe card is arranged above the stage.