When the battery power is down and the unit not plugged in the computer is forced into a sleep mode requiring pushing the start button when power is re-connected. The initial desktop screen appears to be greyed out and is unresponsive with a timer bar which, when the timing sequence is complete restores an active desktop. I can't find any reference to this phenomenon in the OSX literature I have. Any pointers to where I can get more information? Perhaps I am using the wrong search criteria?
This is analogous to hibernation where the contents of the RAM are cached to the hard drive. This allows for the unit to be completely off, but without any loss to currently used data. This only occurs in extreme battery situations.
Apple calls it Safe Sleep.