Flatbed optical drive control The SCB sends a signal (CRMOT) to the flatbed motor to drive the flatbed optical unit forward to scan from the glass, or backward when scanning from the ADF frontside. HP-S is the flatbed home position detection sensor. When the flatbed optical unit is in the home position, a signal (HP-S) is sent to the SCB. Figure 49. Flatbed optical drive control 82 Chapter 5 Theory of operation C8523-90921