What happens when a Laseractive LD is played in a Laserdisc Player

I'm not sure what you were expecting.

It will display this for the first hundred frames or so and refuse to go any farther until it's manually forwarded, then proceeds to play the contents of the disc as a normal Laserdisc. I don't know what the digital track sounds like 'cause the digital read on my player's broken, but I would guess that you'd be met with whitenoise.

 

Does the NEC LD-ROMs also display the same message?

 

No idea. I only own the one disc.

 

I think that the Digital Tracks contain the data for the console, like DTS in LaserDisc.