Samsung Electronics 5-31Circuit Description5-6-10 Cover Open Sensing(+24V)“Cover Open Sensor” is placed on the left top ofPrinter. If the front cover is open or Developer unitis placed in, the Printer does not operate.5-6-11 Paper Sensing(+5V)There are three Sensors for the paper in the Printer:1) Paper Empty SensingIt is placed in Paper Cassette, and senses if thereare papers in Cassette.2) Paper Feed SensingIt is placed before Transfer process, and senses ifthe paper is feeding. When the paper feeding issensed by it, Printer image data is output to LSU.3) Paper CheckIt is placed on the side of paper path. Whennarrow paper(width is more than ???mm) isfeeding, the paper don’t touch the actuator, and itis sensed the narrow paper. The Printer Enginecheck resistance of Transfer Roller and thefeeding paper, if the feeding paper width isnarro w, THV according to the resistance outputshigher voltage than wide paper.4) Exit SensingIt is placed in the exit of Printer, and senses thepaper exit.5-6-12 LSU ControlLSU is composed of a polygon mirror motor and alaser gun part. The polygon mirror motor startsrotation by ‘PMOTOR” signal and reaches theconstant speed, “LREADY” signal outputs “High”from LSU. And when video image signal fro mVideo Controller is applied to Laser Gun, it fire thelaser beam. And the polygon mirror reflects andscans the beam horizontally. When the scanned laserbeam reaches at the side of LSU, “HSYNC” outputsone pulse. Video controller synchronizes this signal,and outputs the left edge of image.5-6-13 Toner CheckToner sensor is placed in the rear of Developer unitto check the toner supply. During warming up andprinting, the controller checks the output signal oftoner sensor. If toner is sufficient, the output signalof †oner sensor is High, and if not, the output signalis Low. When the output signal of toner sensorremains low for more than 5 seconds, controllerjudges. Toner is insufficient, and displays ‘Tonerlow’. In toner low condition, the printer printsapproximately 300 sheets. Then the controllerdisplays ‘Toner Empty.’