How to Update EHS Firmware
Log into the web GUI of the phone.
Navigate to Setting > Preference in the top menu.
Find the option called Zero Touch Type.
Set the Zero Touch Type option to EHS, and press the Save Set button at the bottom of the page.
Navigate to Function Keys > Line Key in the top menu.
Program a spare button to be Zero Touch, set the label to be something like "EHS," and press the Save Set button at the bottom of the page.
You can now press the new EHS button you programmed, and it will start the upgrade process for the EHS adapter.
You have 5 seconds to press the OK button to start the upgrade process.
Press the Start button.
Your current version of EHS software will be shown. You will need to disconnect the EHS adapter and plug it back in. Then, the process of updating will start automatically.
The screen will tell you when the update is done. After the update is complete, you can press Cancel.