APC UPS Serial Signalling Cables - what's so special about them?

[sundew]

I've got an older APC Back-UPS 600 I'm using for my machine, and I'm using a standard serial cable for communication. According to APC I need their "special" signalling cable to have the UPS communicate with my serial port. What is so special about these cables?
Are the pins switched around like a crossover cable? Does anyone know? I've not seen the info on APC's website, but maybe I just missed it.

TIA

[nilknarf]

There's a difference between the BackUPS and SmartUPS signalling, which I've verified requires a different cable. On the BackUPS, however, I think a standard serial cable works. You can always try it and see. If the UPS came with software, or you have their software, the cables usually are included.

I think they do have some of the pins switched around, but I don't know which ones.