John, interesting you should mention that standard. When I was in Ohio we had an interesting Digital multiplexer box on the house, providing 2 lines over one pair, when I measured the input voltage, I was amazed to find over 270 volts from the exchange pair [Linked Image]
The reason we were 'fiddling' was to get the phone co to remove it so we could get ADSL, but that level of voltage scared me.