Using Second Display as Customer Display


I have instaled Sambapos on the Maschine on this Link. In fact it is working well.
It has 2 Screens.

Developper said: Our mainboard is EDP+LVDS, second screen connect com port name is com1

I cannnot communicate with this screen with following Commands
echo testing123>COM1
echo testing123>COM2
echo testing123>COM3
echo testing123>COM4
echo testing123>COM5
echo testing123>COM6
echo testing123>COM7
echo testing123>COM8

I would like to show on this second screen information for customers. Items and Price.

What i am doing wrong?