A DC to DC converter to convert an input voltage to an output voltage. A transistor in which an oxide semiconductor layer containing indium, titanium, and zinc is used as a channel formation region and a semiconductor device including the transistor are provided. The occupant protection device may include an airbag module having an airbag and be arranged at a rear of the seat to be deployable rearward for protecting an occupant situated behind the seat. The second organic emissive layer is disposed between the anode and the cathode, and is adjacent to the first organic emissive layer. A gripping member may be positioned on an outer surface of the fitting tube.