Hi Bob, I found the schematic I use for "complete" null modem, thought
you might be interested in it (complete meaning not just crossing over
TX and RX and connecting GND).        Eric
 
 
   NULL MODEM CONNECTOR
   --------------------
 
                       |- DSR
DTR -------------------|
                       |- DCD
DSR -|
     |------------------- DTR
DCD -|
RTS --------------------- CTS
CTS --------------------- RTS
TXD --------------------- RXD
RXD --------------------- TXD
GND --------------------- GND
 
        DB-9    DB-25
SIGNAL  PIN #   PIN #
---------------------
DCD      1       8
RXD      2       3
TXD      3       2
DTR      4       20
GND      5       7
DSR      6       6
RTS      7       4
CTS      8       5
RI       9       22
--- QM v1.00
---------------