Thank you for your response.
When I connect U2414H to PC via HDMI, graphic drivers default settings are limited range - colours and especially black are washed out, which is visible in comparison to correct setting full range. So definitely monitor is expecting full range and doesn't change this just from being connected by HDMI.
But I was wondering if there is something specific in HDTV broadcast from DVB-C (which I guess is always limited 16-235 range) that can tell to the monitor that it should switch to limited levels. Black from HDTV signal looks sometimes "not black enough" for me but I'm not sure without comparison.
Do you have any idea how to properly test it without any special device? Of course there is no limited/full switch in the DVB-C box and I don't have separate TV display to visually compare colors and black.
Not sure where service tag number is.