Xerox FaxCentre 2121 Service Manual page 184

General Procedures and Information
• When the printer receives a PRINT signal, the polygon motor and the main motor start rotat-
ing and the paper is taken up and fed into the printer.
• The printing is started when the CPU sends a VIDEO signal to the ROS a given period of time
after the leading edge of the paper actuates the paper feed switch (TOD signal).
• The print start position for the 2nd line is defined by delaying the time, at which the VIDEO
signal is to be transmitted.
• The start of scan sensor provided in the ROS ensures that the laser beam is emitted at the
same timing for all lines in the main scanning direction.
Laser Emission Timing
• When a READY signal is detected a given period of time after the print command has been
issued, the CPU outputs a laser ON signal.
• The laser ON signal causes a laser beam to be emitted and the laser beam travels to the pol-
ygon mirror, G1 lens, and the SOS mirror to eventually hit the SOS sensor, which generates
an SOS signal.
• The SOS signal determines the laser emission timing for each line in the main scanning
direction.
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Figure 2
11/06 FaxCentre 2121/2121L