Laguna III Speed Pulse Wire

Im currently fitting a Digitax Mater to my Laguna, however part of the fitting requires that a wire is connected to the speed pulse wire at the back of the radio.



There is not much reference on the net regarding the iso diagram for the Laguna III audio.



Any help would be greatly apreciated as to which wire it is.



Thanks.



Its a 2011 Lag 3 Tom Tom Dymanique if that helps