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 Modems often have a set of eight DIP switches for configuring.
 They usually look like this:

 - - _ _ _ - - _
 1 2 3 4 5 6 7 8

   1. Should be UP so that DTR (Data Terminal Ready) is
      obeyed.  Otherwise the modem ignores the computer when
      it lowers DTR to request a hang up.  This can later be
      overridden with the &D2 command.

   2. Should be UP to request verbal result codes such as
      CONNECT or BUSY rather than incomprehensible numeric
      codes.  This can later be overridden with the V1
      command.

   3. Should be DOWN so that the modem presents result codes
      to the commands it receives.  If it were UP, the modem
      would play dumb and give no responses whatever.  This
      can later be overridden with the Q0 command.

   4. Should be DOWN so that the modem does not echo commands
      back to the computer.  If it were UP, the modem would
      back-talk every command the computer gives it along
      with the result of the command.  This can later be
      overridden with the E0 command.  Some software may
      require this switch to be UP.

   5. Should be DOWN to suppress auto answer.  THIS IS VERY
      IMPORTANT.  Even if you send a modem init string
      containing S0=0 to suppress auto answer, your modem
      will still answer the phone during the interval between
      when it is first powered on and when you first run your
      modem software.

   6. Should be UP to have normal DCD -- Data Carrier Detect.
      Otherwise your modem will lie to your computer that the
      other modem is still attached and working even when it
      has hung up.  This can later be overridden with the &C1
      command.

   7. This should usually be UP for normal single-line
      phones.  It should be DOWN for multi-line phones.  You
      can later override this with the &J0 command.

   8. This should be DOWN to enable the modem's intelligence.
      If it were UP, the modem would totally ignore all the
      commands you send it -- emulating an old-fashioned dumb
      modem.