Xerox 4400DT - Phaser B/W Laser Printer Service Manual page 454

Paper Jam Detection
The base printer and the Stacker are designed to move a sheet of paper between the
detecting points, i.e., sensors, on the paper path within specific periods of time. If a
sheet of paper is either early or late arriving at any point, the Engine Logic Board
interprets this deviation as a paper jam.
E6-1 Jam — The specified time that the paper has to turn the Stacker Sensor
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Assembly Low after it has turned the Sensor Exit High. If the Sensor
Assembly Exit does not go Low after the specified time, the Engine Logic
Board detects that a Stacker jam has occurred.
E6-2 Jam — The specified time that the paper has to leave the stacker
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sensor, or the Stacker Exit Sensor is actuated at power-on.
Phaser 4400 Laser Printer Service Manual 8-41