Xerox Phaser 6121MFP Service Manual page 72

Theory of Operation
Position Detection
2-30
The Toner Cartridge Rack stop position for each color of toner is detected by the
Rack Positioning Sensor. Openings around the circumference of the Toner
Cartridge Rack actuate the Rack Position Sensor at each stop position.
The Magenta Toner Cartridge includes a slit for detecting the standby position.
When the Toner Cartridge Rack is rotated, the Rack Positioning Sensor (PS5)
detects the standby position slit. To bring the toner cartridge rack to a stop at the
corresponding developing position, the rack is rotated from the standby position
62° degrees by the Rack Motor.
Rack Positioning
Sensor (PS5)
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Phaser 6121MFP Service Manual