Abstract: A holder for a stack of sheets which can be fed therefrom in successive cycles from the bottom of the stack and returned to the top of the stack or, in the last cycle, discharged to a tray. The holder includes a separator which can be engaged between the sheets of the stack for separating returned sheets from the other sheets of the stack. A detection system is provided for detecting sheets that have been placed in the holder (for starting a first cycle) and for detecting when all of the sheets have been returned to the holder (for starting a next cycle). The detection system includes a light source and a light sensitive detector installed at the bottom of the stack. When, by the feeding of sheets, the separator reaches the bottom of the stack, the separator intercepts the light from the light source to cause a signal from the detector. This signal is similar to the signal of the detector when the holder is empty, but which signal differs from the reaction of the detector when a sheet intercepts the light.