OK, I will admit my ignorance and probably embarrass myself for a lack of aircraft systems knowledge but I have to ask this question:

The search for the Malaysian jet is now going on in the middle of the Indian Ocean. The news media says that is based on "satellite data" and they keep showing some huge "arcs" that are supposedly based on satellites and they talk about the 7 hours of data that kept coming in after the ACARS and transponder were turned off or quit transmitting, etc. etc.

What system are they talking about? What emitter is there on a 777 besides ACARS, transponder and the radios? They seem to be implying that engine data continues to be transmitted and I know the new generation Boeings all sing like a bird the entire flight, but I always thought that data was transmitted through ACARS? I know ACARS can send via VHF, HF or SATCOM but its all still ACARS, which was supposedly turned off. Is there another system that I'm not aware of?