Weird phone icon?

[ScottG]

I have a Hitachi G1000 Pocket PC Phone. In the last 3 days, I noticed a new, never-before-seen icon in the upper right-hand corner of the dialer screen (in the white area, below where the time displays). The icon looks like a black phone handset just to the left of a black, unlocked padlock. The manual doesn't show this icon at all.

Any idea what it means? :|