Interesting on the phone lines, so I did a bit of reading. The voltage is a -48vdc. To ring the phone, they impose 90VAC over the line, and when you are talking the AC ripples back over the DC and is decoded into speech. There is only about 20 milliamps of current in the DC line and is essentially used for signaling the devices for the AC to do it's job.
Not sure about the high voltage DC stuff. It is interesting tho, but doubt much will happen soon to convert the grid.
I use quite a few LED lights in control systems, mainly for push buttons and indicator lights. I have an indicator beacon here for testing from Banner Engineering. This thing is brighter than a 1000volt xenon strobe light. Plus, they are pretty cool.
