A signal processing device has a memory in which a digital image signal is stored, and a data bus including a plurality of signal liens is connected to the memory. A pull-up resistance is connected to a predetermined signal line, and the other signal lines are connected to the ground through pull-down resistances. A blanking signal BLK3 at a low level is inputted into an output enable terminal of the memory, so that the output terminal of the memory becomes high-impedance, and thus a digital signal corresponding to a pedestal level is outputted through the data bus and a blanking period is formed. The pedestal level is determined by the position of the pull-up resistance.