Brother HL-1870N - Cassette Sensor; Paper Empty Sensor; Paper Eject Sensor

CHAPTER 3 THEORY OF OPERATION
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2.3.5 Cassette sensor / Paper empty sensor
Detect if the paper cassette is installed. They also detect if there is paper in the paper
cassette.
Fig. 3-28
2.3.6 Paper eject sensor
Detects if paper is ejected from the fixing unit.
Fig. 3-29
Cassette sensor PCB assy
Feed MP unit
Eject sensor PCB assy
Fixing unit