Viega Multiplex Trio E Instructions For Use Manual page 22

Handling
Screw the filter into the corner valve.
Connect the hoses of the hot and cold water inputs of the mixing
unit to the respective corner valves.
Seal the hoses for connecting the bathtub and the hand shower
(2 x R ½ x G ½ with union nut).
Screw the hoses to the outputs of the mixing unit for bathtub and
hand shower.
Connect the battery to the control electronics.
Make sure that it is properly aligned. Push the battery in until you
feel the plug snap into place.
Multiplex Trio E fitting, electronic mixing unit 22 from 38