Google "Single-wire earth return" (SWER) for a diagram and explanation - as
others have said, it uses earth grounding for the return path.

http://en.wikipedia.org/wiki/Single-wire_earth_return



wrote in message
...
On Feb 24, 10:45 am, Evan wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.