2400 BPS Pocket FaxModem  (250-3105)     Pinouts       Faxback Doc. # 5763

Serial Connector Pin Assignments

Pin   Label    Description                      Direction

1     N/A      Protective ground                N/A
2     RXD      Received data                    to faxmodem
3     TXD      Transmitted data                 from faxmodem
4     RTS      Request to send                  to faxmodem
5     CTS      Clear to send                    from faxmodem
6     DSR      Data set ready                   from faxmodem
7     N/A      Signal ground (common return)    N/A
8     RLSD     Received line signal detector    from faxmodem
9     +12v     Alternate power source           to faxmodem
20    DTR      Data terminal ready              to faxmodem
22    RI       Ring indicator                   from faxmodem

PIN

1 - PROTECTIVE GROUND

2 - RECEIVED DATA (RXD), INPUT  The DTE uses RXD to send data to the
                                faxmodem for transmission over the
                                telco line or to transmit commands to
                                the faxmodem.  The DTE should hold
                                this circuit in the mark state when no
                                data is being transmitted or during
                                intervals between characters.

3 - TRANSMITTED DATE (TXD), OUTPUT  The faxmodem uses the TXD line to
                                    send data received from the telco
                                    line to the DTE and to send
                                    faxmodem responses to the DTE.  In
                                    command mode, TXD data represents
                                    the faxmodem responses to the DTE.

4 - REQUEST TO SEND (RTS), INPUT  The DTE uses this line for control
                                  signals to the faxmodem.

5 - CLEAR TO SEND (CTS), INPUT  The faxmodem uses this line to send
                                control signals to the DTE.

6 - DATA SET READY (DSR), OUTPUT  The faxmodem uses this line too, to
                                  send control signals to the DTE.

7 - SIGNAL GROUND

8 - RECEIVED LINE SIGNAL DETECTOR (RLSD), OUTPUT  When AT&C0 command
                                                  is not in effect,
                                                  RLSD output is ON
                                                  when a carrier is
                                                  detected on the
                                                  telco line or OFF
                                                  when carrier is not
                                                  detected.  RLSD can
                                                  be strapped ON using
                                                  the AT&C0 command.

9 - 12v, INPUT  This line carries +12v to power the faxmodem, when
                used with a PC-compatible computer whose DB-25
                connector supplies +12v to this pin.  The faxmodem is
                not harmed by the absence of 12v on this pin.

20 - DATA TERMINAL READY (DTR), INPUT  The DTE uses this line to
                                       control the faxmodem.  The
                                       setting of the &D command
                                       determines how this line is used.

22 - RING INDICATOR (RI), OUTPUT  RI output ON (low) indicates the
                                  presence of an ON segment of a ring
                                  signal on the telco line.  (The
                                  ring signal cycle is typically two
                                  seconds.  ON, four seconds OFF.)
                                  The OFF (high) condition of the RI
                                  output is maintained during the OFF
                                  segment of the ring cycle (between
                                  rings) and at all other times when
                                  ringing is not being received.

For the fax portion of your faxmodem to work with a Macintosh computer, it
is important to have the right cable connecting he faxmodem to the
computer.  Many cables labeled "V-series", "MNP cable", or "High-speed
modem cable" will not allow faxing to work.  The following commonly
available Mac-to-modem cable (sometimes called a "regular" cable), will
work:

Mac Mini-DIN            Faxmodem 25-pin Male

Pin 1          to       Pin 20 (or pins 4 and 20)
Pin 2          to       Pin 5
Pin 3          to       Pin 2
Pin 4 and 8    to       Pin 7 (or pins 1 and 7)
Pin 5          to       Pin 3
Pin 6                   (no connection)
Pin 7                   (no connection)

(smc-01/10/94)