How to factory reset a Cisco 8840 8841 8845 88XX
- Unplug the handset
- Keep pressing the "#" button while connecting the power cable (or Ethernet if using PoE)
- Leave the "#" button when only headphones and speaker icon turn green
- Press in sequence: 123456789*0#
- The line buttons will flash amber and green as the phone start the reset process
- Phone will reboot several times and it will be factory reset