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An Intel 80960SA computer chip controls both the memory and the printing
mechanism in the printer, called the print engine. The printer stores a whole
page in RAM before printing it. (If a page is so dense that it overflows
memory —amost unlikely event —the Star LaserPrinter4HI prints the page
on two sheets.)
1.1.5 The Print engine
It's the print engine that forms the actual characters and graphics. The engine
directs its laser, a pinpoint stream of light pulses, through mirrors and lenses
onto the surface of a positively-charged rotating drum.
r"i""r
Lens
Laser beam
Scanningmirror
ctor laserdiode
~Photosensitive
drum
As the laser scans, it "draws" the page-map stored in your printer's memory.
Wherever a light pulse strikes, that tiny part of the drum drops to a neutral
electrical charge. That spot then attracts fine toner powder as the drum rotates
past the powder compartment.
As the drum rotates further it meets the paper. The paper itself is negatively
charged by passing by a fine corona wire. Since opposite charges attract, the
negative paper clings to the positive drum. Then heat and pressure from a
roller melt or,fusethe dots of toner onto the paper, precisely reproducing the
image.
Finally the paper slides into the output bin. The paper usually comes out face
dowmso it stacks in the correct sequence.
4
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