Emergency message test

[aaronwt]

I saw my first Emergency message Saturday night at 8:30 PM. I was recording IceAge2 at the time from Comcast on HBO or SHowtime and the message came up, overlayed over the programming. I couldn't change the channel but the TiVo continued to record. After a few minutes the message disappeared . The show was still recording and I could change to the other tuner again. The recording was never interrupted and the message was not in the recording so the TiVO just overlayed it on the screen and had nothing to do with the recording.
Is this normal? I thought I had read that when this happens the recording stops and doesn't start again. This seemed to act the way I would expect it to. It didn't affect the recording, only my ability to change the channel during the warning.

[GoHokies!]

From my (extraordinarily limited) understanding, there are different levels of alerts, some just overlay the data, while others force a tune to a particular channel.

It would make sense that a test would be the lowest level, least intrusive type of alert that could be sent out.