The VISUALISER button is one of the buttons that selects the input going into the projector.  The VISUALISER button does not turn on the local VISUALISER, this needs to be done using the on button on the top of the Visualiser. (exceptions to this are in Waterfront LT1 and LT2 where selecting VISUALISER does turn the Visualiser on.

The button panel controls the AV switcher in the desk rack.  The VISUALISER input can be selected using the AV switcher if the local button panel is not working.