
          C H O O S I N G   A   M O D E M
          
          There are two kinds of modems--internal and external.   
          
          
          INTERNAL MODEMS
          
          An internal modem is actually a modem and a serial port
          (COM port) built on a printed circuit card. This printed
          circuit card fits in a slot inside your computer on what
          is known as the mother board and uses the computer's
          power supply.
          
          The advantages of an internal modem are: 
          
              1.  They are usually less expensive to buy.
          
              2.  They fit inside the computer and, therefore,
                  don't take up extra desk space.
          
              3.  They contain both a modem and a COM port, so
                  you don't need to purchase another COM port
                  (called a serial card) if your computer
                  doesn't have one available.
          
          The disadvantages of internal modems are:
          
              1.  They often are much harder to set up for the
                  novice.
          
              2.  You are more likely to have conflicts with
                  internal modems.
          
          My advice to beginners is to have a competent computer
          dealer (or local "guru") install an internal modem. 
          
          
          EXTERNAL MODEMS
          
          External modems come housed in their own chassis and have
          their own power supply.
          
          The advantages of an external modem are:
          
              1.  They are easy to set up. All you do is plug
                  in some cables and connect the modem to an
                  existing serial port using a modem cable.
                  Usually, COM1 is set up for your mouse, and
                  COM2 is a good port for plugging in an external
                  modem.
          
              2.  They don't take up a slot on your computer.
          
              3.  They will work with all kinds of computers,
                  including desktop computers and laptops.
          
              4.  They are easy to move from one computer to
                  another.
          
              5.  External modems have status lights that
                  inform the user what is going on (if you have
                  read your modem manual).
          
              6.  They have a speaker built-in, and most allow
                  you to easily control the volume.
          
          You will need to know which COM port your modem uses when
          you install telecommunications software.  Determining COM
          port usage is addressed later in this section.
          
          
          
          
          MODEM COMPATIBILITY
          
          Today, most modems are Hayes-compatible and this is what
          you will want. The majority of the almost outdated 2400
          baud modems use a CCITT (Consultive Committee on
          International Telegraphy and Telephony) standard of V.22
          bis. With a name like that you can see why they prefer to
          use an acronym. 
          
          The faster 14,400 baud modems use V.32 bis/V.42 bis. The
          bis is a compression technology that packs data into a
          smaller space. MNP (Microcom Network Protocol) levels 1
          through 4 and V.42 are error correction protocols. 
          
          MNP 10 is an error correction protocol for use with
          cellular modems. For more about "V." terms, see the
          glossary of Telecommunication Terms.
          
          
          
          MODEM SPEED
          
          If you plan to use your modem for downloading lots of
          files, you will want to look at the faster modems with a
          baud rating of 14,400 bps or more. If a file takes one
          minute to transfer at 14,400 bps, it will take at least
          six minutes to transfer at 2400 bps. Actually, a modem
          can achieve a greater throughput than it's rated speed
          when you consider data compression. Throughput is the
          rate of useful data sent--considering data compression. 
          A modem with data compression (V.42 or V.42 bis) should
          be set for a terminal speed of four times the modem's
          rated connect speed. That means a 14,400 bps modem should
          be set to 57,600 baud. A 14,400 bps modem under ideal
          circumstances can achieve a throughput rate of 57,600
          bps, resulting in much greater efficiency. To achieve
          this, the auto-baud option must be turned off in your
          modem software. Turning the auto-baud feature off
          effectively locks the port speed to what you set it for
          in the modem software. This is sometimes referred to as
          "locking the port speed."
          
          The prices on faster modems have fallen dramatically in
          the last year. You can now buy a 14,400 bps modem with
          built-in fax capability for considerably less than
          $70.00 (at discount stores). Some of the new modems can
          be upgraded using software.  
          
          If you buy a high speed modem and want to transfer data
          faster than 19,200 bps, you will need a special 16550-
          compatible UART chip in your serial port. A fast internal
          modem will already have such a chip built-in. If you have
          a fast external modem, you can purchase a serial card
          with a buffered 16550 UART chip for around $50.00 from
          your favorite super computer store. The latest in fast
          modems are called V.34. These modems support
          a baud rate of 28,800 bps. Many of these faster modems
          support a built-in fax, caller ID, and voice mail!
          
          The newer V.34 modems require a specially equipped serial
          card to handle the high speed data flow. An internal
          modem already has such features built in.

          Hayes is offering an Enhanced Serial Port card, equipped
          with a buffered UART 16550 chip, a coprocessor, and more
          memory, to handle their new line of super fast external
          modems.  
          
          
          TIP
          
          If your modem has MNP 5, you may want to turn it off when
          downloading a compressed file. MNP 5 is a data
          compression protocol. The MNP 5 protocol does not
          recognize data that is compressed (for example a .ZIPped
          file), so it wastes time trying to compress data that is
          already compressed. This can really slow down a download.

          To turn off MNP 5, you will need to consult your modem
          manual. The V.42 bis does recognize compressed data, so
          there is no need to turn V.42 bis off.    
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