From the user manual but beware you will need all the details to set it up from scratch:
HandyTone-486 User Manual Grandstream Networks, Inc.
8 Restore Factory Default Setting
Restore the Factory Default Setting will erase all configuration information of the device.
• Step one: Find the MAC Address of the device. The MAC address of the device is located on the bottom of the device. It is a 12 digits hex number.
• Step two: Encode the MAC address to decimal digits. The encode rule is:
“2” is the first letter on the button “2” so its encoding is “2”.
“A” is the second letter on button “2” so its encoding is “22”.
“B” is the third letter on button “2” and its encoding is “222”.
“C” is the fourth letter on button “2” and its encoding is “2222”.
For example, for MAC address 000b8200e395, the
user should encode it as “0002228200333395”.
• Step three: Access the voice menu, then dial “99” and get the voice prompt “RESET”
• Step four: Key in the encoded MAC address decimal digits after hear the IVR prompt. Once the correct encoded MAC address is keyed in, the device will reboot automatically and restore the factory default setting.
• Be advised by default the HT486 WAN side HTTP access is disabled. After the factory reset, the
ONLY way to get access to the configuration page is connecting your computer to the LAN
port of HT486.