This is a summary of the information we have so far.
Original cable
PC end (Female.)
1 (DCD) (in) Brown
2 (RX) (in) Red
3 (TX) (out) Yellow
4 (DTR) (out) Brown
5 (SG) Green
6 (DSR) (in) Brown
7 (RTS) (out) Blue
8 (CTS) (in) White
9 (RI) Not used
DTR is linked to DCD and DSR (Brown wire.)
---------------------------------------------------------
Plotter end (Male)
1 (DCD) (in)
2 (RX) (in) Yellow ?
3 (TX) (out) Red ? (- Ve)
4 (DTR) (out) ( ???)
5 (SG) Green ?
6 (DSR) (in)
7 (RTS) (out) (+ve)
8 (CTS) (in)
9 (RI) Not used
---------------------------------------------------------
As DTR, DCD and DSR are linked together at the PC end we know it is not a standard null modem cable.
More clues would be helpful.
Looking at the cable side of the male connector that was on the plotter end of the cable are there any pins linked together ? Are there any pins that have NOT had wires soldered to them ?
Is there any voltage (+ or -) on these pins of the connector on the plotter. 1, 4, 6, or 8 Even a very small voltage would indicate that there was hardware on the plotter to use that pin as an input. (But it still may not be used by the software.
Les.