An AM transmitter having tracking power supply compensation. The LED control section sequentially drives the two LEDs, LED1 and LED2, on the basis of an image pickup start timing signal corresponding to each image pickup cycle S for the CCD within the image pickup cycle S such that driving time periods for LED1 and LED2 do not overlap. Upon reaching the lifted position, retention features on the lift mechanism and the battery module engage to hold the battery module in the lifted position. Accordingly, there is obtained a semiconductor memory device in which a reduction of a read margin is suppressed. A housing is received in a third compartment and a flexible bladder is disposed in the housing and is in fluid communication with the fourth compartment. According to the invention, the pushing or pulling device is mounted on a sliding carriage that can be moved on the side beams along the longitudinal axis of the side beams by means of a drive unit mounted on the sliding carriage.