Digitizers
Digitizers, which are also calleddigitizing tablets,drawing tablets, or justtablets, are draw-
ing tools that capture the movements of the operator’s hand. Their operation is similar to
thatofamouse,buttherearemajordifferences.Theinputfromamouseisalwaysrelative
to where the cursor is on the screen. If you draw a line with a mouse and then pick up the
mouse and move it to a different position on the desk, the input will continue from the last
position of the cursor. However, a digitizing pad relates each position on the tablet to a
specific position on the screen. This makes it possible to accurately trace an existing drawing,
or to create original drawings, such as an architectural design, which must correspond to
precise dimensions.
A digitizer is made u pof two main com ponents: an electronic tablet and one of two
types of drawing devices. One type is apen(also called astylus), which is held like an or-
dinary pen and used to “draw” directly on the tablet. These movements are captured and
translated into a corresponding drawing on the PC. The other type of drawing device is
called apuck(or acursor), which closely resembles a mouse and is used in much the same
way. A small window with crosshairs makes the puck ideal for very precise tracing of ex-
isting drawings. In both cases, the tablet detects the exact position of the drawing device
and sendsxandy(left and right and u pand down) coordinates to the PC. Pens and pucks
are available with and without cords.
Like scanners, digitizers connect to the PC in a variety ways. Most digitizers connect
through a proprietary controller card. There is no standardization among the types of ca-
bles used between theses proprietary interfaces and the tablet, so the manufacturer must
be contacted for replacements should one become necessary. Some digitizers use the se-
rial port, with one end of the connecting cable attaching to the PC with a standard DB-9 or
DB-25connector.However,theotherendofthecable,theoneconnectingtothedigitizing
tablet, is usually a proprietary connector. There are newer models that now use a USB or
IEEE 1394 connectors as well.(^566) PC Hardware: A Beginner’s Guide