I'm new to this board, but have enjoyed it for a while. Let me try to solve the mystery. My TL has the same button. I had a grapple installed. To operate the grapple jaws, you have to have the functional equivalent of a third circuit on the loader. To accomplish this the dealer installed a diverter. This device mounts on the forward cross member on the loader and acts to divert the flow of hydraulic oil when you want to operate the grapple jaws. The circuit that is being interrupted controls bucket roll. The way you control the diverter is by pushing the BUTTON on the joystick. The TL joysticks I've seen are black in color and that is probably a dead button. When a diveter is installed, the button is replaced with an operational button (mine is red, to continue the self destruct theme). When you push the button in with your thumb and move the joystick side to side, your grapple jaws open and close. As soon as you remove your thumb from the button, your roll function operates. It is very easy to use and really makes the grapple productive. The electricity is provided by an auxilary circuit that plugs in just behind and outboard of the seat.