Originally Posted by
imagineertobe
You're both getting towards the right answer.
In this photo you'll see two ticket machines side-by-side. The one on the right accepts Euro bills, as you can see it has been made a little wider by the addition of a bill-accepting unit. Not all machines are like this, and not all stations are equipped with a bill-accepting machine.
Peace.
All of the station I visited have machines that take coins only. Do the station agents make change? [I haven't seen any bill changers in the metros, only at cdg.]