Lexmark MS911 Service Manual page 645

For print jobs that do not require finishing, the paper is fed on top of the HPT. The sensor (HPT bin full) detects if the
bin is full.
# Part
1 Sensor (HPT bin full)
2 HPT feed sensor actuator
3 Sensor (HPT feed)
4 Sensor (HPT door)
5 Motor (HPT transport)
6 HPT transport rollers
Appendix C: Theory of operation
645
4021, 7421