Gemini Printer User Manual page 88

Gemini User's Manual
Paper
"Needle" pin
Sprlng
Clapper
Platen
r
Pln gulde
'IL
$- Iron core
I
I
Ribbon guide
\'
Bobbin
Printer solenoid
Figure 6-2. This side-view schematic of the print-head mechanism shows
how electrical signals to the solenoid cause the clapper to "fire" the
needle-like pin that impacts the ribbon/paper/p/a ten. After the solenoid
releases the clapper, a spring returns the pin to its original position.
Gemini's built-in "computer" reads the ASCII code
instructions sent by your computer and directs the print head to
discharge the correct pins in the proper order. The result of this
"hiring" and "firing" is the printed characters produced by Gemini _
onto your paper.
Consider, if you will, the process of printing an uppercase
letter "H" (see Figure6-3). Because the print head is bidirectional
(can print right to left, and left to right), Gemini can start the "H"
from either side.
In this example, the top seven pins fire simultaneously to print
one side of the letter. Then, the print head moves across the paper,
and pin number four fires three times to create the horizontal line.
Finally, the top seven pins fire simultaneously again to complete
the othervertical line. Aside from the amazing fact that the entire
printing operation just described can take place in approximately
one-hundred and twentyth of a second, all this activity is
caused by a single ASCII code signal.
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