It is true that for televisions, signals are detected. However, monitors are a little different in that they only accept certain resolutions. Check the manual to make sure that the resolution you're sending to the television matches with one of the resolutions that the monitor can display.
I am no expert. I just bought a Samsung T240hd TV with built in freeview. I also bought a Panasonic DMR-EZ48VEB DVD and VHS combi recorder and player. I have managed to get the TV to work by itself and watch all the freeview programs. I set up the DVD according to instructions. The two are connected with a scart cable and coaxial cable. The aerial is connected into the DVD. Now when I try to play a DVD there is no image on the TV. I try to set the TV input to 'ext' but that does not work. Then the TV needs resetting with the menu to watch TV. I thought that the signal from the DVD, whether form its own freeview tuner, or tape or DVD was automatically detected by the TV. Any Ideas?