DVi_D cable question

on these latest players that upscale to 1080 using a dvi-D connector and y prpb (560) cables.
the question is :
what turns on the 1080 res by way of the cable is it a signel or a internal wire swich

even with the cable connected to the player greys out the 1080 but when its connected to a digital TV it becoms operational.

I know its apears to be a stupid question , but we are trying to build a converter from dvi-D to y prpd with full 1080 so it can be used on CTR Projectors . like the sony g70 /90
we have to simulate what the digital tv does to the player to turn on this hi def.
then the rest can be finished.