Originally Posted by synaesthesia 
Got any official like documentation for that? One of the sites I deal with has a whole room full of kit wired exactly in that manner - I shrieked when I saw it and demanded to know who fitted it :| Guessing it's in the IEEE regs somewhere but my searching skills lack :|
As I mentioned earlier in the thread
http://www.tlc-direct.co.uk/Book/6.6.1.htm