ADF feeder sensors REG-S (registration sensor): detects when paper is approaching the registration rollers. TMG-S (timing sensor): verifies that paper is moving through the paper path. SKR-S (back skew sensor) SKF-S (front skew sensor) Note The ADF has a document detection sensor that detects the presence of paper. This sensor is not shown in the graphic below. When the sensor detects the presence of paper, the LED on the ADF illuminates. Figure 57. ADF feeder sensors C8523-90921 ADF operation 91