      CHAPTER ONE.  FEATURES AND COMPATIBILITY

INTRODUCTION

      Congratulations!  The Courier modem
      you've purchased represents powerful,
      advanced electronic design that offers
      exceptional reliability, compatibility
      and flexibility at all standard rates up
      to 14,400 bits per second (bps).
      Courier HST modems connect with each
      other up to 16,800 bps.  The
      transmission rate between the computer
      and modem, depending on your equipment
      and software support, can be as high as
      57,600 bps.

      The following features and capabilities
      assure you of superior reliability and
      performance.

   High Speed CallsAdaptive Speed Leveling
   (ASL)

      All Courier high speed modemsHST, V.32
      bis and Dual Standardconnect at 9600,
      12K and 14.4K bps, with 16.8K the
      maximum rate on HST-to-HST connections.
      In addition, our high-speed modems
      monitor phone line quality and perform
      Adaptive Speed Leveling.

      Like most high speed modems, Courier
      modems fall back to the next lower
      speed, for example, 12K, then 9600, if
      poor line conditions warrant.  Unlike
      other modems, however, that stay at the
      lower rate for the rest of the call,
      Courier modems detect improved line
      conditions and shift upward again to the
      next higher speed.  ASL keeps the modems
      online, always operating at the highest
      possible speed, and constantly ensuring
      data integrity.

   Error ControlV.42/MNP

      Data integrity is ensured when the
      modems connect with remote modems that
      use the V.42 (LAPM), USR-HST, or MNP
      error control protocols.  Error control
      is available on calls at 1200 bps and
      above.

   Data CompressionV.42 bis/MNP5

      Data compression enables potential
      throughput of well over  50K bps on
      14.4K or 16.8K bps connections.
      Couriers connecting under V.42 or HST
      error control use V.42 bis compression.
      Couriers connecting under MNP error
      control use MNP Level 5 compression.
      Achievable throughput of text and other
      types of files is listed in Appendix A.
   Flow Control/Variable Interface Rates

      Flow control, required under error
      control, also allows the local computer
      interface rate to be set higher than the
      link rate, enabling greater efficiency
      and throughput.  If your equipment and
      software support high rates, data can be
      sent from the computer to the modem at
      57.6K, 38.4K or 19.2K bps, regardless of
      the link rate.

   Voice/Data Switch

      Users have always been able to phone and
      make arrangements with another user
      before turning control of the call over
      to the modems.  A new feature, a switch
      on the modem's front panel, allows you
      to change from voice to data and back
      again, without issuing a command.

      If you don't ordinarily use voice and
      data in the same call, you can assign
      the switch a different function that
      normally requires a command, such as
      resetting the modem.  See Appendix E,
      Voice/Data, for instructions on
      voice/data switching.

   Trellis Coded Modulation

      At speeds above 7200 bps the Courier
      uses trellis coded modulation.  This
      technique makes high speed data
      transmission less vulnerable to errors
      caused by the phone network.  The modems
      can tolerate twice the amount of noise
      in the telephone channel than they could
      with conventional modulation (quadrature
      amplitude modulation, or QAM), so there
      are fewer error control retransmissions.
      Trellis coded modulation is also less
      susceptible to impulse-type noise.

   Asynchronous/Synchronous Capability

      Courier high speed modems operate
      synchronously as well as asynchronously.
      A personal computer equipped with a syn-
      chronous interface adapter can call
      computers that use standard synchronous
      protocols.  See Chapter 7 for more
      information.

   Programmable Nonvolatile Memory

      You can tailor your own default settings
      and store them in nonvolatile random
      access memory (NVRAM).  Each time the
      Courier is powered on, it operates at
      the settings you've specified.
   Link Rate Negotiation

      The Courier automatically lowers its
      link rate to match a lower rate of a
      remote modem, in both Originate and
      Answer Modes, allowing connections with
      a wide range of installed modems.

   Link Diagnostics

      After each call, you can display a Link
      Diagnostics screen containing
      information about the last call,
      including the number of data characters
      transferred, line statistics, the call's
      rate and the reason the call was
      disconnected.

   Modem Diagnostics

      New CCITT V.54 loopback testing with the
      &T command options, and earlier Courier
      Register S16 test options are available.
      The modem performs three loopback tests:
      analog, digital, and remote digital.
      See Appendix F for information.

   Inactivity Timer

      You can set the modem to automatically
      hang up after a specified number of
      minutes if there is no activity on the
      phone line.

   Call Duration Reporting

      The modem records the duration of your
      calls in hours, minutes, and seconds.
      This feature enables you to display and
      print an audit of your calling
      activities.  You can optionally use the
      modem clock as a real-time clock.
   Call Progress Detection

      An optional set of result codes (screen
      messages) lets you know when a line is
      busy, a person rather than a modem has
      answered the phone, there is no dial
      tone, or the distant phone is ringing.

   Modem Settings Displays

      On command, the modem displays its
      current settings, a handy way to check
      your transmission rate, S-Registers and
      other operational controls.  The modem
      also displays the defaults stored in
      nonvolatile memory and the factory
      defaults stored permanently in read-only
      memory.

   HELP Screens

      The modem displays screens that
      summarize the command sets, Dial command
      options, and S-register functions.

   Bottom Panel Reference

      Command summaries and other information
      are printed on the bottom of the modem
      case.  A Dual In-Line Package (DIP)
      switch guide makes it easy to tailor the
      switch settings to your terminal or
      software requirements.

   Dialing the Last Dialed Number

      The modem has a buffer that stores each
      dialed number until it is cleared by
      another Dial command.  A few keystrokes
      cause the modem to redial the number in
      the buffer without your having to enter
      the number again.
   Automated Redialing

      You can put the modem into Repeat Mode
      to continuously redial if a previous
      dial attempt fails to connect.  This is
      especially useful in dialing services
      whose lines are often busy.

   Quote Mode

      Set the modem to Quote Mode if you want
      it to dial an alphabetic acronym instead
      of a numeric number.


COMPATIBILITY

      The Courier adheres to the following
      standards, ensuring compatibility with a
      wide base of installed modems.  Unless
      otherwise indicated, HST, V.32 bis and
      Dual Standard modems all conform to the
      listed standard.

       USR-HST   16.8K,
                 14.4K/12K/9600/7200/4800 bps
                 (Dual Standard and HST
                 modems)
       CCITT V.32 bis    14.4K/12K/9600/7200/4
                 800 bps (Dual Standard and
                 V.32 bis modems)
       CCITT V.32   9600/4800 bps (Dual
                 Standard and V.32 bis modems)
       CCITT V.22 bis    2400 bps
       Bell 212A 1200 bps (also CCITT V.22)
       CCITT V.23   1200 bps with 75 bps back
                 channel (British phone
                 system)
       CCITT V.25   Answer sequence for calls
                 originating outside the U.S.
                 and Canada
       Bell 103  300 bps (CCITT V.21 optional)
       CCITT V.42   LAPM error control, 1200
                 bps and higher
       CCITT V.42 bis    Data compression,
                 1200 bps and higher
       MNP       Levels 2, 3 and 4 error
                 control, level 5 data
                 compression, 1200 bps and
                 higher
       CCITT V.54   Analog, digital and remote
                 digital loopback testing
 
      Other compatibility features include the
      following standards and certification:

          Can be used with any computer or
           terminal that is compatible with
           the RS-232 standard interface.
          Can be used with any computer or
           terminal that uses ASCII, the
           standard character code supported
           by most equipment manufacturers.
          Connects with older systems whose
           equipment operates at rates varying
           between 110 and 300 bps.
          Connects in synchronous mode at
           standard rates with any system
           using a synchronous protocol
           compatible with your synchronous
           interface equipment.
          Is fully FCC- and DOC-certified for
           the uses described in this manual.
         
