diagram for a three phase Y 120/208 transformer bank hook-up and a single phase 120/240 off the same bank.
That would look like the old style peace symbol back from the days of the Vietnam War. Center tied to ground. I don't think any POCO does it though. You could have 120V with both sides hot by connecting say the inverse A phase (here I call the vertical line from the top to the bottom of the peace symbol phase A, bottom of this line "inverse A") to phase B or C. Why anyone would want to do that is another question, even if code allowed it. If a customer had some 240V loads he might want such service from phase A.
