The only difference in mine was using a dead laptop power supply to power the telephones instead of batteries. Like it is appreciated in the picture I drilled a hole on a plastic electrical box and pushed the wire through. I made a knot to avoid someone yanking the wires of the phone jack by accident.
The 20 volt transformer came with just one white colored wire and another braided wire around this single wire. I assumed that the white wire was the "live" or negative charged wire and the braided uninsulated wire was the "neutral" or positive wire. I was pleased to discovered that I was correct.