Oki ES3640MFP Component Replacement Manual page 24

The diagram below identifies the paper feed sensors.
Job Offset
Trailing Edge
Sensor
Side Output Tray
Stack Full Sensor
Job Offset Home
Position Sensor
Paper Size Switch
OHP Sensor
MPT No Paper
Sensor
No Paper Sensor #2
Registration Sensor #2
Top Output Tray
Stack Full Sensor
Side Output Tray
Detect Sensor
Feed Out
Sensor
Transfer Unit
Entrance
Sensor
Registration
Sensor #1
Tray 1 Level Sensor
Tray 1 Low Paper Sensor
MPT Level
Sensor
Feed Out
OHP Sensor