- last post: 01.01.0001 12:00 AM PDT
It's a transmission.
However, I, like Zag, don't think Cortana is actually transmitting anything; it's just there to add another layer of suspense to the trailer and serves no purpose but to break the fourth wall. I think the fact that the Master Chief appears to be ignoring Cortana is evidence to this theory.
[Edited on 6/17/2006]