Iiyama ProLite TF1534MC User Manual page 15

 Touch Input Settings in Dual Screen Mode
Connect the primary monitor to the computer first.
Set Control Panel > Hardware and Sound > Tablet PC Settings > Display > Setup.
The following message will appear on the screen. Please follow the instructions.
After setting , connect a second monitor and perform the setup as in
The monitors are recognized as dual-display, and touch operation cannot be performed on
NOTE
two monitors at the same time.
You can perform touch operation on only one of the monitors.
.
BEFORE YOU OPERATE THE MONITOR 11