ASPEN TECHNOLOGIES, INC.

28.8EFX

Modem Type                   Data (synchronous/asynchronous)/Fax
Maximum Data Rate            28.8Kbps
Maximum Fax Rate             14.4Kbps
Data Bus                     External
Fax Class                    Class I & II
Data Modulation Protocol     Bell 103A/212A

                             ITU-T V.21, V.22, V.22bis, V.23, V.32,
                             V.32bis, V.34

                             Rockwell V.FC
Fax Modulation Protocol      ITU-T V.17, V.21CH2, V.27ter, V.29
Error Correction/Compression MNP5, V.42, V.42bis

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                                CONNECTIONS

         Purpose             Location          Purpose           Location

  Line out                     CN1       DC power                  CN4

  Line in                      CN2       Power switch              SW1

  RS-232/422                   CN3

                             DIAGNOSTIC LED(S)

    LED         Color         Status                 Condition

     MR          Red            On                  Power is on

     MR          Red            Off                 Power is off

     TR          Red            On               DTR signal is high

     TR          Red            Off              DTR signal is low

     SD          Red         Blinking        Modem is transmitting data

     SD          Red            Off        Modem is not transmitting data

     RD          Red         Blinking         Modem is receiving data

     RD          Red            Off         Modem is not receiving data

     OH          Red            On               Modem is off-hook

     OH          Red            Off               Modem is on-hook

     CD          Red            On            Carrier signal detected

     CD          Red            Off         Carrier signal not detected

     AA          Red            On              Auto-answer enabled

     AA          Red            Off             Auto-answer disabled

     AA          Red         Blinking             Phone is ringing

     HS          Red         Blinking         Modem is in test mode or
                                                 detected an error

     HS          Red            On          Modem is operating at 9600bps
                                                     or faster

     HS          Red            Off         Modem is not operating faster
                                                    than 9600bps

                         Proprietary AT Command Set

               See document V1535 for a full command summary.