Here's how the HS34 audio out will work:
The D100 and D120 will still make the noises they make today.
The HS34 will also make all of those noises that come out of a D100/D120 or convert them to voice alerts (your choice).
Basically, if you have the HS34, we recommend hooking only that up to your intercom. If you hook the D120 and/or D100 up at the same time, you'll get a bunch of sounds at once.