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Photosensors
Photosensors, monitored by the DC Controller, are responsible for
detecting the presence of paper, paper motion, and timing. (See
Table 5-2.) Photosensor PS2 senses paper in the PC tray;
photosensor PS4 senses paper in the MP tray. The message PC
LOAD or MP LOAD is displayed when either the PC tray or the MP
tray is selected as the primary tray and is out of paper. PS6 and
PS7 (respectively) sense the presence of paper in the Lower
Cassette and the Envelope Feeder. Paper must be loaded into the
primary paper tray before printing can resume. The message PC
EMPTY or MP EMPTY is displayed when either the PC tray or the
MP tray is out of paper and is not selected as the primary paper
tray. LC EMPTY or EE EMPTY is displayed when the Lower Cassette
or the Envelope Feeder is empty. The EMPTY message is only a
reminder that the paper tray is empty; it is not necessary to load
paper to continue printing from another tray.
The Paper Control PCA, Lower Cassette Assembly, and the
Envelope Feeder communicate with the DC Controller through
serial data lines. The condition of the printer engine
photosensors PS2, PS4, PS5, the optional Lower Cassette PS6,
and the optional Envelope Feeder PS7 is encoded into a digital
logic stream and read by the DC Controller on line SLI.
PS1 detects paper at the Input Feed Roller and is used in jam
detection and registration. PS3 detects the presence of paper in
the Fuser Assembly, and is used in jam detection. PS5 terminates
laser operation when it detects the end of the sheet. This allows
the printer to print images on odd-sized media fed from the MP
tray without contaminating the Transfer Roller.
Note
The LaserJet 5 printer uses different tray
designators and associated messages as follows.
LJ 4 / 4 Plus LJ 5
MP Tray Tray 1
PC Tray Tray 2
LC Tray Tray 3
MP/PC/LC LOAD TRAY x LOAD (x=1,2, or 3)
MP/PC/LC EMPTY TRAY x EMPTY (x=1,2, or 3)
5-6 Functional Overview