Setup guide

23
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United States/Latin America
One Magnum Pass
Mobile, AL 36618
[phone]*
Fax [phone]*
Latin America Fax [phone]*
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Canada
Saint-Laurent, Québec
[phone] or [phone]
Fax [phone]
National Service Fax [phone]
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Europe, Middle East, Africa
Düsseldorf (49) 211/596 1333
London (44) 784 430900
Maarssen (31) 3465 51 333
Paris (33) (1) 4107 9393
Stockholm (46) (8) 725 5680
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Auckland 64 (9) 630 7912
Melbourne 61 (3) 899 5777
Sydney 61 (2) 901 3235
Tokyo (81) 3-3437-4030
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Because of the way MS-DOS and computer hardware are
designed, any time you attach or install a serial device (like a
fax-modem board) you have to figure out which COM setting
to configure the new device for. (“COM” is the name MS-DOS
uses for serial communication ports.) Each serial device must
have a unique COM setting, one that isn’t used by anything
else in the computer.
But most likely, one or more of the four COM settings MS-
DOS provides (COM 1, COM 2, COM 3, and COM 4) was
already assigned to something in your computer before it
even left the factory. (For example, any serial ports you see
on the back of your computer are probably using COM set-
tings, even if they’re not connected to anything.)
You also have to remember that, generally, you can only have
two COM settings in use at one time. COM 1 and COM 3 usu-
ally can’t both be in use at the same time, because normally
they’re both set up to use the same IRQ setting (IRQ 4). The
same goes for COM 2 and COM 4, which share IRQ 3. (IRQ
stands for Interrupt ReQuest. Every device used by the com-
puter, whether it’s a serial device or not, is assigned an IRQ.)
It is possible to use both 1 and 3 or both 2 and 4, if the new
serial device can be configured to use a “non-standard” IRQ
(an IRQ other than 3 or 4), and if this non-standard IRQ is not
assigned to anything else in the computer. (Check the serial
device documentation to find out if the device supports IRQs
other than 3 and 4. To find out if these non-standard IRQs are
available in your computer, you can use Microsoft Diagnos-
*The 205 area code chan
g
es to 334 on Januar
y
15, 1995.