THE following ASCII schematic is for connecting a SupraFAXModem to a
"dumb" device which transmits data to the modem periodically regardless
of the carrier state.  This schematic assumes that the device is configured
as a DCE device, and so pins 2 and 3 are crossed between the two ports.

       MODEM DB25                            FIRE ALARM DB25

          |\                                          |\
          |  \                                        |  \
Pin 2     | @----> (P6 on LCA127E)  /------------------@   | Pin 2
          |    |                  /                   |    |
Pin 3     | @-------------------/   (P4 on LCA127E) <--@   | Pin 3
          |    |                                      |    |
          |    |                                      |    |
Pin 7     | @----------------|-------------------------@   | Pin 7
          |    |             |--> (P2 LCA127E)        |    |
          |    |                                      |    |
          |    |   ____     _____                     |    |
Pin 8     | @-----|____|---|___|||--> (P1 LCA127E)    |    |
          |    |   1K       1N4148                    |    |
          |    |   1/4W                               |    |
          |   /                                       |   /
          | /                                         | /

                       LCA127E Optical Coupled Switch

                             _____    ______
                            |     \__/      |
                     Pin 1 ==               == Pin 6
                            |               |
                     Pin 2 ==    LCA127E    == Pin 5    (No Connection)
                            |               |
 (No Connection)     Pin 3 ==               == Pin 4
                            |               |
                             ---------------

Note: 1.) Pin 2 of the modem DB25 ties to pin 6 of the LCA127 only.
       
      2.) Pin 3 of the modem DB25 ties to pin 2 of the FA DB25 only.

      3.) Pin 7 of the modem DB25 ties to pin 7 of the FA DB25 and also
          to pin 2 of the LCA127.

      4.) Pin 8 of the modem DB25 ties to a 1K resistor in series with
          a 1N4148 diode with the cathode (the striped end) of the diode
          connected to pin 1 of the LCA127.

If you are unable to find the LCA127 IC try a NTE3085 (the pin-out is the
same), also most standard LED input opto-isolator with a low impedance
output state when triggered (that will switch both possitive and negative
signals) should be usable.  (A solid state relay with very low current
trigger requirements might also work.  A standard relay could also be used
to get the same result, however, a power source would have to be provided
that would be switched on and off by the low current carrier detect signal
available on pin 8 of the modem.)

Use this as a modem init. string: AT&F2&KS0=1&D&W&W1

                                           dumb_dev.txt v1.2 (phm 6/1/94)