asterisk users - May 2003 - TDM400P FXO port polarity on RJ45

I notice that on the TDM400P I have here the polarity of the FXO port
(only position 1 is fitted on this card) is inverted compared to what
you would find on a normal wall FXO outlet. Anybody know if this was on
purpose and, if so, what the thinking was ?

Incidentally, I bought one of those polarity checkers a while back
thinking it would be a handy fast way to check. Only problem was that
the polarity checker was wired wrong so now I have to remember RED=GOOD,
GREEN=BAD... sigh......