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Modems and
Faxes
Modems let you link your computer to the outside
world. Connected properly, you can use a modem to send data and
files to anyone else with a modem and a computer. You can also
access information and download it for use on your PC.
This chapter explains what a modem is, and how to
set one up for use with your PC. In addition, you learn about using
a modem as a fax machine and how to troubleshoot modem problems.
Understanding Modems
A modem is a hardware device that lets two
computers exchange information over telephone lines. Using a modem,
you can connect directly to another computer that is also equipped
with a modem, to an online service provider such as America Online,
or to the Internet and World Wide Web. When you're connected, you
can send and receive files or communicate in real time--which
means you communicate with little or no delay, as if you were
face-to-face with the person at the other computer.
Modems let you communicate over standard
telephone lines with other com- puter users. You can transfer data,
exchange electronic files, and even carry on a typed conversation in
real time.
These days, a modem is a vital part of a PC;
without one, you'll miss out on a wide range of opportunities.
Here's a small sampling of things you can do with a modem:
Exchange data
directly with other computer users.
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Access an
online service or the Internet to gather information or to
distribute information about anything, anywhere.
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Exchange
electronic mail.
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Play
interactive online games.
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Make hotel or
airline reservations.
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Check stock
prices. |
The word modem is actually an abbreviation
of the terms modulator-demodulator, which describe how a
modem works.
Here are the basic steps involved in transferring
data using modems:
- 1. Software in your computer activates the modem, which
listens on the phone line for a dial tone, then dials a
specified number.
2. The receiving modem on the other end answers the call
and sends out a signal which the sending modem recognizes,
establishing a connection.
3. The modem sending information converts the computer's
digital signals into analog signals that can be sent over the
phone lines (this is called modulating).
4. The receiving modem translates the incoming data back
into digital signals that its computer can understand (this is
called demodulating).
5. When the online session is over, the computers issue a
command telling the modems to hang up.
In order to make a connection using a modem, you
need the following:
Access to
a telephone line. Modems have two jacks where you plug
in standard telephone cables. You use one jack to connect
the modem to the telephone line, and the other jack to
connect the modem to a phone.
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Data
communications software. You need software to control
the modem. Data communications software issues commands such
as telling your computer when to dial and when to hang up.
It also lets you set communications parameters such as the
data transfer rate. The software must be compatible with
both the modem and your PC. (Windows 95 comes with a basic
data communications software called HyperTerminal.)
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Software
drivers. You must have the necessary drivers for the
modem to work with your operating system. Windows 95 comes
with drivers for most modems. |
Choosing a Modem
Choosing a modem is not as difficult as choosing
some other computer components because there is less variety. There
are two basic types of modems:
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Internal.
These are hardware boards you plug into an expansion slot in
your PC's system unit. Internal modems are convenient
because they don't take up desk space, and they use the
computer's power supply so they are on whenever the computer
is on. |
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An internal modem plugs into an
expansion slot inside your PC. The phone jacks are acces-
sed through a port on the back of the system unit.
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External.
These are connected to the PC by plugging a cable into a
port on the system unit. External modems also have their own
power cords. You must turn on the modem when you want to
make a connection. One benefit of an external modem is that
you can move it to another computer if necessary. |
An external modem has controls and status
lights on the front that you can use to monitor transmissions.
NOTE:
You can attach a telephone to either kind of modem
so when you are not using the modem, you can use the phone to make
regular calls.
Aside from choosing an internal or external
modem, the other main factors to consider are:
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Communications
speed. A modem's speed, called the baud rate, is
measured in bits per second (bps). Currently, speeds range
from 300 bps to 56Kbps, but to satisfy the need for speed,
manufacturers are developing faster modems all the time. |
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Cost.
The faster the modem, the higher the cost--although faster
transmission times may save you money on your phone bills.
Also, external modems generally cost about $30 to $50 more
than internal modems. For example, a 56Kbps internal modem
will probably cost between $100 and $200. A 56Kbps external
modem would range from $150 to $225. |
NOTE: If you only use your modem to send and receive
e-mail
messages, you may be able to get by with a modem as slow as
14.4Kbps. If you use your modem to transmit and download files, or
if you like to surf the World Wide Web--which uses a lot of
graphics images--you should purchase the fastest modem available.
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Communications
software. Most communications software programs have
features for storing telephone numbers as well as for
automatic dialing and answering. Even more important, you
use the communications program to set communications
parameters, which are the rules the modem uses to make
the call and transmit the data. You want to choose a modem
that supports the communications parameters you plan to use. |
NOTE: The communications parameters set for the sending
modem must match the communications parameters set for the
receiving modem.
Modems also operate under communications
parameters. Modem communications parameters include:
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Transmission
speed. As mentioned earlier, speed can range from 300
bps and up.
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Transfer
protocol. This helps to make sure the data the modem
transfers is error-free. Common transfer protocols include
XMODEM, YMODEM, and ZMODEM. The Internet uses FTP (File
Transport Protocol), and some online services have their own
transfer protocols. For example, CompuServe uses CompuServe
B.
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Data
format. This is usually text for unformatted text files,
and binary for graphics or formatted text files.
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Compression
standard. This allows modems to compress data before
transmitting it, effectively increasing transmission speeds.
Common compression standards include MNP 5 and CCITT
V.42bis. |
Selecting a Fax Modem
One final consideration when purchasing a modem
is whether or not you want fax capabilities. Because most modems
currently available include fax capabilities, it's not much of a
decision. Fax modems generally don't cost any more than standard
modems, so in addition to using the modem to communicate with other
computers, you can use it to communicate with facsimile machines.
With a fax modem, you can:
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Transmit
standard computer files to a receiving fax machine.
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Receive fax
transmissions and store them as computer files. |
NOTE: If you already have a stand-alone fax machine, you
do not have to use the fax options on the modem. The device will
work fine as a plain modem.
To use the fax capabilities, you need to have
specific fax software or data communications software that includes
fax support.
Connecting a Modem
Connecting a modem involves attaching the modem
device to your PC and to the telephone line. The modem should come
with the necessary equipment, including a standard RJ-11 telephone
cord. The steps you take depend on whether you have an internal
modem or an external modem.
If you have an internal modem, you must install
it by removing the cover of the system unit and plugging the modem
card into a vacant expansion slot. Unless you are extremely
confident about working inside your computer, you should have the
modem installed by a professional computer technician.
If you have an external modem, however, you can
easily connect it yourself. To connect an external modem to your PC,
follow these steps:
- 1. Locate the serial cable that came with the modem. It
should have a 25-pin male connector at one end and a 25-hole
female connector at the other end.
2. Plug the female connector into an open 25-pin serial
port on the PC's system unit, and plug the male connector into
the modem device.
3. Secure the connectors using the screws on either side.
4. Locate the power cord for the modem device and plug it
into an electrical wall socket, power strip, or uninterruptible
power supply.
After the modem is connected to your PC, you must
connect it to the phone line. This procedure is the same for both
external and internal devices.
To connect a modem to the phone line, follow
these steps:
- 1. Locate the two phone jacks on the modem, labeled Phone
and Line. They will be on the outside of an external
modem, or on the back of the system unit if you have an internal
modem. They look just like the phone jacks on your telephone.
2. Plug one end of a standard RJ-11 telephone cord (it
should come with the modem) into the Line jack, and the other
end into the wall jack for your telephone.
3. Plug one end of another RJ-11 telephone cord into the
Phone jack, and the other end into your telephone.
TIP: If you have a phone line dedicated for use with
your computer, you do not need to connect the modem to the
telephone. You only need to connect to a phone if you want to be
able to use the phone for regular calls when the modem is not in
use.
Understanding Your Modem
Controls
An internal modem is integrated into your PC; you
will interact with it using your data communications software. If
you have an external modem, however, you can control and monitor
certain functions on the device itself. For example, status lights
on the front of the modem let you know whether the modem is on, and
whether it is in send mode, ready to dial and transmit data,
or receive mode, ready to answer and download data.
If you look at the front of your external modem,
these are some of the controls you are likely to find:
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Power On
light. An external modem must be turned on in order to
work. When you press the on/off switch, the power light will
come on.
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Speed
indicator. Most modems can operate at different speeds;
this light tells you which speed is currently in use.
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Mode
indicator. If you have your modem set to answer an
incoming call, the Answer mode indicator will be lit. If it
is set to dial, the Dial mode indicator will be lit.
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Error
indicator. If there is a problem with the transmission,
the Error light will be on. |
Be sure to read the documentation that comes with
your modem for complete instructions on understanding the modem
controls and status lights.
Setting Up Your Modem to
Work in Windows 95
Windows 95 uses the Install New Modem Wizard to
help you identify and set up newly installed modems. Before starting
the wizard, it helps to know the manufacturer and model of the
modem. Also, if you have an external modem, make sure it is turned
on.
To use the Install New Modem Wizard, follow these
steps:
- 1. Double-click My Computer and then double-click the
Control Panel folder icon. Alternatively, click the Start
button, then open the Settings menu and click Control
Panel.
2. Double-click the Modems icon in the Control Panel
folder to open the Modems Properties dialog box. Click the Add
button to start the Install New Modem Wizard, then choose Next.
3. Windows 95 immediately tries to detect and identify
the modem. When it does, it displays the Verify Modem screen of
the wizard, displaying the name or type of modem that it finds.
It also identifies the communications port where the modem is
connected. If the information is correct, choose Next, then
choose Finish.
4. If Windows 95 cannot detect the modem, the wizard
displays a screen where you can select the modem information
yourself. (You can display the same screen by clicking the Change
button if the information on the Verify Modem screen of the
wizard is incorrect.) Select the modem's manufacturer in the
Manufacturers list box. Select the specific modem in the Models
list box, then choose OK.
NOTE: If your modem is not on the list, choose the
Standard Modem Types manufacturer and select the model according
to speed. Or, click the Have Disk button and follow the
instructions to install a vendor-supplied driver.
- 5. Choose Next, then choose Finish. Windows 95 installs
the necessary drivers for the modem, then closes the wizard.
Choose Close to close the Modems Properties dialog box.
- On the Verify Modem page of Windows 95's Install New Modem
Wizard, you see the port and modem type Windows has detected.
Click Change to select a different modem.
NOTE: If Windows 95 detects the new device when you
first turn on your PC, it will prompt you to run the Add New
Hardware Wizard to detect it and set it up. Go ahead and use the
Add New Hardware Wizard; it performs the same function as the
Install New Modem Wizard, but will detect and set up other types
of hardware devices as well.
Troubleshooting Your Modem
When a modem doesn't work, there could be
problems with the hardware, the communications software, or the
software settings. Here are a few tips for locating the problem and
fixing it.
The External Modem Isn't
Working
If your external modem is not working, here are a
few things to check:
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Make sure the
modem is turned on.
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Make sure the
cables between the modem and the computer attached correctly
and securely.
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Make sure the
modem power cord is plugged in.
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Make sure the
modem is set to the correct mode. Use Answer mode if you are
trying to receive a transmission, or Dial mode if you are
trying to initiate a transmission. |
The Modem Dials, but
Doesn't Connect
If your modem dials, but doesn't connect, here
are a few things to check:
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Make sure
both the sending and receiving modems are set to the same
communications parameters.
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Make sure the
modem is dialing the correct number. If another modem
doesn't pick up on the other end, the call can't go through.
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Make sure
there isn't interference on the telephone line. Modems are
more sensitive to static and other interference on a line.
Someone picking up an extension phone, crossed wires, even
thunderstorms in the area can cause enough disturbance to
cancel a call. Make sure the line is clear, or try a
different phone number. |
The Modem Doesn't Get a
Dial Tone
If your modem doesn't get a dial tone, here are
some things to check:
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Make sure the
RJ-11 telephone cords are connected correctly. You may have
the Phone jack connected to the telephone line, and the Line
jack connected to the telephone.
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Make sure the
telephone is working.
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Make sure
your communications software is correctly installed.
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And in some
cases with pulse dial de-select in modem properties wait for
tial tone before dialing |
Windows or the
Communications Software Displays a Message Saying It Can't Find the
Modem
If Windows or your communications software
displays a message telling you that it can't find your modem, here
are some things to check:
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If you have
an external modem, make sure it's plugged in, that the cable
is attached securely to the port on the system unit, and
that the device is turned on.
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Make sure the
correct driver is installed. If necessary, run the Install
New Modem Wizard again.
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Make sure the
COM port setting is correct. If the modem is set up with
COM1, but Windows 95 thinks it's in COM4, Windows won't be
able to find it. Check the COM port setting on the
Properties page of the Modems Properties dialog box, and
make sure it is the same as the COM port setting in your
communications software.
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The interrupt
request (IRQ) setting may be conflicting with another
device. This is a relatively technical problem, and you
should have a qualified technician look into it.
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Check for an
IRQ conflict. To do so, from the Start menu, choose Settings,
Control Panel. Click the System icon, then click the
Performance tab of the System Properties dialog box. The
status area of this tab will report an IRQ conflict if one
exists. You're not advised to try to fix this conflict, but
the information will help you accurately report the problem
to a technician.
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The modem may
be damaged. Have a technician check it out.
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