Theory of Operation 8-249Sensor Location and FunctionNo. Sensor Function1. MPT Entrance Sensor Detects incoming paper to determine the timing forswitching from hopper to carriage.2. OHP Sensor Detects the presence or absence of transparencymedia.3. MPT Empty Sensor Detects paper present in the MPT.4. Black Toner Cartridge SensorDetects full, low, and empty state of tonercartridges.5. Y Yellow Toner Cartridge Sensor6. Magenta Toner Cartridge Sensor7. Cyan Toner Cartridge Sensor8. Top Side Output (Face-Up) Sensor Detects paper exit to determine the timing for joboffset operation.9. Stack Full Sensor Detects the height of the stack of prints in theFace-up tray (top output).10. Exit Sensor Detects the leading and trailing edges of media anddetermines whether the paper has exited theprinter.11. ADC Sensor (Color RegistrationAssembly)Measures the density pattern printed on the transferbelt.12. ATS Sensor Adjusts the fuser temperature according to thethickness of media loaded in the tray.This only functions when the front panel media typeis set to plain or letterhead.13. Temp/Humidity Sensor Board Measures the printer’s temperature and relativehumidity in order to calculate the optimal transfervoltage under the current environmental conditions.14. Transfer Belt Entrance Sensor Detects the beginning of media transfer and basedon the time it takes to for the leading edge to reachthe sensors, determines media length.15. Registration Sensor Determines job offset.16. Entrance Sensor Determines movement of media through the printer.17. Waste Toner Full Sensor Detects a full state of waste toner in the transferbelt waste toner bin.18. Tray 1 Paper Empty Detects the absence of media in the tray.19. Tray 1 Low Paper Detects a low condition of media loaded in the tray.20. Door A Open Switch (Interlock) Detects a right door open condition and shuts offthe +34 volt supply.21. Top Cover Open Switch Detects a top cover open condition and shuts offthe +34 volt supply.
