Why all the craziness with custom serial cables?
It was nothing more nor less than a form of customer control. For a long time APC wanted to keep other people from talking to its UPSes so it could lock out potential competition for its PowerChute software. Scrambling the leads on its serial cables was a cheap way to accomplish this – in fact, they tended to be wired so that if you tried a straight-through cable, opening a serial link to the UPS would be interpreted as a shutdown command! (Hardware companies often think like this – they lock up interfaces by instinct, cornering a small market rather than growing a bigger one. It’s fundamentally stupid and self-defeating, but it’s the kind of stupid that tends to sound good at an executive meeting.) Fortunately, APC has lost a lot of this attitude since about 2000; nowadays they even release technical information to the apcupsd maintainers.
