I'll give you half an answer. I've done some experiments concerning the ID battery power on an old 920 I have. I found that when the unit is not plugged in, the battery is feeding voltage to the IC chip holding the ID number. However, when the unit is plugged in (wall or ups, as long as its 120 volts ac), there is 5 volts being feed to the IC chip. So, my guess is that if the 922 has a similar power circuit as the 920, then power will be fed to the IC chip as long as 120 volts ac is available to the unit. Maybe if someone has a broken 922 they can test this out for sure. Good Luck.