(^434) PC Hardware: A Beginner’s Guide
Thermal printers use a resistance ti pthat heats u pwhen electricity flows through it.
The resistance in the printhead of the thermal printer is very small and heats up and cools
down in a fraction of a second. Using the heated resistance as a stylus, the thermal printer
moves over the thermal paper to create text through a series of dots.
The thermal paper is treated with a chemical that reacts to a moderate temperature by
changing color. The color varies by the type of paper, but generally the paper turns a dark
gray (white paper) or white (dark paper). In contrast to the dot matrix or inkjet printers,
the thermal printer’s printhead doesn’t have any moving parts, so only the printhead
movessidetosidetoprint.Becauseathermalprinterrequiresverylittlepowertoheatthe
resistance element, they are lightweight, portable, and can even run on batteries. A real
advantage to a thermal printer is that they are virtually silent in operation.
Thermal printers are typically used in specialized applications, such as server stations
in restaurants, where their lack of noise is a plus. They are also used on a great many cash
registers, and have been popular for portable printers for notebooks and other portable
PCs.However,theinkjetprinterisquicklybecomingamorepracticaldeviceforthelatter.
The paper is the real drawback to a thermal printer. To the paper, heat is heat without
regard to its source. Any heat source can discolor the paper, which tends to make a ther-
mal printout less than permanent.
Connecting the Printer to the PC
Most PC printers connect through a parallel port, which is usually designated as LPT1. A PC
may have more than one parallel port, but on most systems there is usually only one. The
most commonly used connectors used to connect printers directly to a PC are as follows: 25-pin DB (data bus) female connector The LPT/parallel port on the back of
a PC is usually a 25-pin female connector into which the male connector on the
printer cable is connected. Most PCs only have a single LPT port that is mounted
on the motherboard or an expansion card.
36-pin Centronics This is the common connector on the printer end of
the cable. The PC end of the cable is normally a 25-pin male connector, as
described in the previous bullet. The 36-pin Centronics connector is so named
because Centronics Corporation produced a large share of the early printers.
The connector design was actually developed by Ampenol Corporation. The
Centronics connector is also the standard connector for the HP-IB (Hewlett
Packard Interface Bus) used on all HP printers.
USB (Universal Serial Bus) Some of the latest printers feature a USB
connection in addition to the standard parallel connector. If the parallel port
is already in use by a scanner or Zip drive, the USB port allows the printer to
be connected to the PC without using the parallel port or any additional system
resources. Older printers can be connected via a USB connection using a