Abstract: A single tray or multi tray sheet feed system is provided. A sensor is provided to sense the sheets leaving from the single tray or multi tray system. If the paper weight of sheets of paper on a tray fall within a first range of paper weight values, the sensor is designed to have a first given voltage response condition for sensing these sheets and if the paper weight of the sheets falls within a second range of paper weight values the sensor is designed to have a second given voltage response condition for sensing the latter sheets. A current value supplied to the emitter of the sensor can be controlled to provide the desired voltage response or a resistance in a phototransistor collector circuit can be varied to provide the desired voltage response condition.

Abstract: The sheets in each tray of a multi tray sheet feeder are of the same thickness, but the sheets in one tray may be of a different thickness than the sheets in another tray. The sheets are fed from each sheet feeder tray to an intermediate stacker and then to a printer. A first sensor is provided just prior to entry of a sheet into the intermediate stacker and a second sensor is provided to sense a sheet as it is fed from the intermediate stacker. If the paper weight of sheets of paper on a tray fall within a first range of paper weight values, each sensor is designed to have a first given voltage response condition when sensing those sheets and if the paper weight of the sheets falls within a second range of paper weight values each sensor is designed to have a second given voltage response condition sensing the latter sheets.

Abstract: The thickness of a first sheet fed from each tray of the multi-tray sheet feeder is detected by a first sensor and a thickness value is placed in memory for that tray. Each sheet subsequently fed from the same tray is detected by the same sensor and the thickness value sensed is placed in memory and compared with the thickness value in memory for that tray. When a tray is reloaded, the thickness value in memory for the sheets previously loaded in the tray is erased and the first sheet fed from the reloaded tray is sensed and a thickness value for that sheet is placed in memory for the reloaded tray. After the thickness value of a sheet is sensed by the first sensor, the sheets enter into the intermediate tray. The thickness value of a sheet is detected by an outlet sensor as it leaves the intermediate sheet tray and that value is compared to the thickness value in memory which was detected for the same sheet by the first sensor.