[kelnos]

This might be my bubble showing, but I expect this would have worked better if DC lighting became more popular 20+ years ago, when many many more people had landlines.

(I suppose a lot of people in the US still probably do have landlines, but I know very few, if any, people who do.)

Then again, my house (built in 2009) is still wired for a landline, but the wires (and the voltage on them) remain unused...