Null cable or stright thru?

[TedThompson]

I wish to make my own cable (25 to 9) which wiring protocol is used for the cables being sold as "ADTpro compatible" on the website? It's not mentioned (or I didn't see it)

[david-schmidt]

Hi, Ted - I think you sent this same note to me on RetroFloppy, so I'll just answer it here. The straight-through cable has the following pinout (bog-standard 9 to 25 pin mapping):

DE-9 - DB-25
1 - 8
2 - 3
3 - 2
4 - 20
5 - 7
6 - 6
7 - 4
8 - 5
9 - 22
G - G

The null modem looks like this:

DE-9 - DB-25
1 - 4+5
2 - 2
3 - 3
4 - 6
5 - 7
6 - 20
7+8 - 8
9 - 22
G - G