Page 30 of the manual of studio 192 :
A + B + C. Outputs A, B, and C can all be active at the same time. This setting is useful while mixing in 5.1.
But it s not working for me with pro tools 10 HD or 12 HD. How can to proceed ? The only way is to desactivate the UC CONTROL That is completly different that you wrote in your manual !