Sharp Mobilon HC-4000 Operation Manual page 26

Replacing the backup battery
1. Turn off the unit.
2. Slide the battery replacement switch to the REPLACE BACKUP BATTERY
position.
When the battery replacement switch is set to the REPLACE BACKUP
BATTERY position, pull gently on the main battery holder to see if it is
securely attached. If necessary, attach the main battery holder securely in
place before continuing to the next step.
3. Use a ballpoint pen to open the backup battery cover. Do not use the stylus.
4. Remove the old backup battery with a ballpoint pen.
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