NEC 750C - Manual (Page 25)

2-12 Getting Familiar with Your MobilePro 750C
Replacing the bay cover
NOTE
The unit only operates when the battery cover
lock is in the locked position.
Back-Up Battery
A low battery message appears when back-up battery
power is depleted. Be sure to replace the back-up battery
immediately as described next.
1. When you see the following message, the back-up bat-
tery must be replaced.
Backup Battery Very Low
Save your data, turn off unit power, remove the stylus,
and close the display panel.