Previous MIMO systems have used spatially diverse antenna elements in order not to reduce the number of orthogonal channels that can be realized. A pawl may be movably mounted on the bottom plate and engage latch catch brackets mounted to the top plate to lock the seat in predetermined operator seat positions. If the resulting speed is lower than a reference value which has been set so that an operation to avoid an overflow of a buffer RAM in the image reading apparatus may not be caused, the sub-scanning speed of the image reading apparatus is set lower, and the image is read at the lower speed.