A sheet discharge device includes a sheet discharge path, a discharge portion for discharging the sheet, and a pressing member. In the apparatus, phase information is recorded in the optical recording medium by a phase modulating means for modulating phase of one of the two beams of light. A zero-cross detector circuit monitors the AC input to determine zero-crossings associated with the monitored AC input. The frequency spectrum scan rate is very fast as the settling time for the simple RF front-end is small and the speed of RF switching is high. The process robot has a robot arm vertically moveable along a lift rail. At the individual element manager, based on the selection information from the selection and notification section of the network manager, a control section controls the corresponding subnetwork.