if not wrong, lordie is refering to the isolated outlet from the pedal power. Each outlet is like having its own individual 9v supply to the pedal.
dunlop dc brick is actually like a glorified version of the one spot. Each of the outlet is still tapping from single 9v supply and the outlets on the brick itself, is like the usual dc chain.
for t rex supply, theres 1 model with isolated supply for the 12v outlet only and another 2 different model with individual isolated 9v supply
info from here
http://www.stinkfoot.se/andreas/diy/power/psu.htm