On my 18,when I upgraded the software, the center tone was on by default even though the menu said it was off. The tone at 50% was driving me nuts. To turn it off, I had to go to the menu, turn it on and then exit and go back to the menu and turn it off. Point being, if he had the latest software, it should be on, unless they fixed that. It did the same thing on my DX 9 when I put the latest software in.