Page 70 - DCAP101_BASIC_COMPUTER_SKILLS

Unit 4: Secondary Storage Devices

band printers, therefore, do not have the ability to print any shape of characters, different Notes
sizes of print, and graphics such as charts and graphs.

Figure 4.20: Printing Mechanism of a Chain/Band Printer

Chain/band printers are impact printers because they print by hammering on a paper and
inked ribbon against the characters embossed on the chain/band. Hence, they can be used
to produce multiple copies by using carbon paper or its equivalent. Due to impact printing,
chain/band printers are noisy in operation and often use a cover to reduce the noise level.
Printing speeds of chain/band printers are in the range of 400 to 3000 lines per minute.

Laser Printers
Laser printers are page printers that print one page at a time. Main components of a laser
printer are a laser beam source, a multi-sided mirror, a photoconductive drum, and toner
(tiny particles of oppositely charged ink). To print a page of outpat, the laser beam is
focused on the electro statically charged drum by the spinning multi-sided mirror. The
mirror focuses the laser beam on the surface of the drum in a manner to create the patterns
of characters/images to be printed on the page. Since the drum is photoconductive, a
difference in electric charge is created on those parts of the drum surface that are exposed
to the laser beam. As a result, the toner, composed of oppositely charged ink particles,
sticks to the drum in the places where the laser beam has charged the drum’s surface. The
toner is then fused permanently on. The paper with heat and pressure to generate the
printed output. The drum is then rotated and cleaned with a rubber blade to remove the
toner sticking to its surface to prepare the drum for next page printing. Figure 4.21 shows
a laser printer.

Figure 4.21: A Laser Printer

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