
3COM CORPORATION

AUTO DIAL 21A

Card Type                Modem (asynchronous)
Chip Set                 U.S. Robotics
Maximum Data Rate        1200bps
Data Bus                 External
Data Modulation Protocol Bell 212A

                                                                      54164

                                CONNECTIONS

         Function            Label            Function             Label

  Line out/in - unidentified      CN1      DC power                 CN4

  Line in/out - unidentified      CN2      Power switch             SW1

  RS-232/422                      CN3      Analog loopback switch   SW2

                        USER CONFIGURABLE SETTINGS

                      Setting                         Label      Position

  Auto answer disabled                                SW3/A        Off

  Auto answer enabled                                 SW3/A        On

  CD normal                                           SW3/B        On

  CD forced high                                      SW3/B        Off

  Equalize for dial-up phone lines                    SW3/C        Off

  Equalize for dedicated phone lines                  SW3/C        On

  DTR normal                                          SW3/D        Off

  DTR forced high                                     SW3/D        On

                                  RS232C

        Setting           SW4/A        SW4/B        SW4/C        SW4/D

  Pin 2 receive/Pin 3       On          On           Off          Off
         send

    Pin 2 send/Pin 3       Off          Off          On           On
        receive

  MISCELLANEOUS TECHNICAL NOTES

  Note: Diagram not available.

                             DIAGNOSTIC LED(S)

   LED      Color    Status                    Condition

    CD       Red       On               Carrier signal detected

    CD       Red      Off             Carrier signal not detected

    HS       Red       On            Modem is operating at 1200bps

    HS       Red      Off      Modem is operating at slower than 1200bps

    OH       Red       On                  Modem is off-hook

    OH       Red      Off                  Modem is on-hook

    TR       Red       On                 DTR signal is high

    TR       Red      Off                  DTR signal is low

    RD       Red       On               Modem is receiving data

    RD       Red      Off             Modem is not receiving data

    AN       Red       On                 Auto-answer enabled

    AN       Red      Off                Auto-answer disabled

    SD       Red       On             Modem is transmitting data

    SD       Red      Off           Modem is not transmitting data

    AL       Red       On        Modem is in analog loopback test mode

    AL       Red      Off      Modem is not in analog loopback test mode

    ON       Red       On                     Power is on

    ON       Red      Off                    Power is off

                         Proprietary AT Command Set

                                   ABORT

  Type:          Immediate

  Format:        Any key

  Description:   Aborts dialing command issued; modem hangs up.

                                  ANSWER

  Type:          Immediate

  Format:        AT [cmds] A

  Description:   Enables answer mode, the modem goes off-hook.

                                 ATTENTION

  Type:              Immediate

  Format:            AT [cmds]

  Description:       Tells the modem that a command follows or use alone
                     to test OK result code

                                   DIAL

  Type:                 Immediate

  Format:               AT [cmds] D<#> [cmds]

  Example:              ATDT 443-3388,,,1111;

  Description:          Dials telephone number according to any modifiers
                        included in the string

  Note:                 Any combination of modifiers can be used to
                        produce the desired dial functions in sequence.

        Command                             Function

           P            Pulse dialing enabled

           T            Tone dialing enabled

           ,            Dialing paused for 2 seconds

                                   ECHO

  Type:            Configuration

  Format:          AT [cmds] En [cmds]

  Description:     Controls echo function; display keyboard commands when
                   enabled.

     Command                             Function

       E0          Echo function disabled

       E1          Echo function enabled

                              ECHO - ON-LINE

  Type:           Configuration

  Format:         AT [cmds] Fn [cmds]

  Description:    Selects whether commands sent while in data mode are
                  echoed

    Command                              Function

       F0         Local echo enabled

       F1         Local echo disabled

                              ESCAPE SEQUENCE

  Type:                   Immediate

  Format:                 +++AT [cmds] <CR>

  Description:            Initiates the escape sequence and returns the
                          modem to the on-line command state if it
                          receives three escape characters set in S2
                          within the time allotted by S12.

            Note: Do not precede this command with AT.

                               PULSE DIALING

  Type:              Configuration

  Format:            AT [cmds] P [cmds]

  Description:       Enables pulse dialing

            Note: This command can be duplicated with the P modifier in
            the D (Dial) command.

                          REPEAT PREVIOUS COMMAND

  Type:           Immediate

  Format:         A/

  Description:    Repeats previous command, mainly used for redial

            Note: Do not precede this command with AT, or follow it with
            <CR>.

                                   RESET

  Type:           Immediate

  Format:         AT [cmds] Z [cmds]

  Description:    Resets the modem and clears all registers to default
                  values

                               RESULT CODES

  Type:          Configuration

  Format:        AT [cmds] Qn [cmds]

  Description:   Enables modem to send result codes to the DTE

    Command                              Function

       Q0        Result code sending enabled

       Q1        Result code sending disabled

                            RESULT CODE FORMAT

  Type:             Configuration

  Format:           AT [cmds] Vn [cmds]

  Description:      Selects word or numeric format for information-text
                    and result codes

     Command                              Function

        V0          Numeric format enabled

        V1          Verbose (word) format enabled

                     SELECT CALL PROGRESS RESULT CODES

  Type:               Configuration

  Format:             AT [cmds] Xn [cmds]

  Description:        Enables selection of tone detection and associated
                      result code format options

      Command                              Function

         X0           Extended result codes disabled; result codes 0-4
                      enabled.

         X1           Extended result codes enabled; result codes 0-5
                      enabled

                               SPEAKER MODE

  Type:          Configuration

  Format:        AT [cmds] Mn [cmds]

  Description:   Selects various speaker options

    Command                              Function

       M0        Speaker disabled

       M1        Speaker enabled until carrier signal detected

       M2        Speaker enabled

                              STATUS-REGISTER

  Type:                  Configuration

  Format:                AT [cmds] Sn=x [cmds]

  Description:           Writes to a specified register, values ranging
                         from 0-255.

        Command                              Function

          S0=x           Sets the number of rings allowed before the
                         modem automatically goes off-hook.

                         S0=0 will disable auto-answer.

          S2=x           Selects a character used for the escape
                         sequence.

                         Default = 43

          S7=x           Maximum wait time in seconds the modem uses
                         after dialing to detect a carrier signal from
                         the remote modem for both originating and
                         answering calls.

                         Default = 30

                               TONE DIALING

  Type:              Configuration

  Format:            AT [cmds] T [cmds]

  Description:       Enables tone dialing mode

            Note: This command can be duplicated with the T modifier in
            the D (Dial) command.

