Paper feeding system

In a paper feeder for use in a copying machine equipped with a plurality of trays for storing paper of various sizes;

• the improvement comprising:
• a circuit for encoding a selected paper size from a number of available paper sizes;
• circuit means for detecting and encoding the sizes of paper stored in the plurality of trays;
• a comparator circuit for comparing said selected paper size with one of the plurality of trays that contains paper corresponding to the selected paper size;
• and
• a dual discriminator circuit for generating signals in response to the output of said comparator circuit, said discriminator circuit in a first mode enables paper feeding from a selected tray if paper is available for feeding and in a second mode generates a signal to indicate necessity of adding paper to the selected tray if the tray is empty.