The yyyy_firmware_1.8.x.0.sysupgrade file is used to update the firmware through the 
Upload Firmware menu option.

For update part 2:
For anyone running 4.1.26.0 or lower, we now have a new boot loader, so we need to update the core file.
The .core file is used to update the maintenance files via the "Support" menu option.
The .core file will, unless you uncheck the "Confirm operations from keypad checkbox", ask for confirmation by pressing a button on the controller.
The forcereset file will reset the outlets.

If the right side firmware is 1.7.27.0 or higher, you can use one of the .avr files.
update_x.x.x.x.avr  should not reset the outlets, but there is a chance that the update may not show as successful.
update_x.x.x.x_forcereset.avr  version WILL reset any ON outlets, but the update is assured.

If the current right-side firmware is lower than 1.7.27.0, then use the .core file to update.

If you try the non forcereset version, and after the update you don't see that the AVR (maintenance) version has changed, logout and login again. Then recheck the right-side version.
It's possible that it may still be updated and will show after a power cycle or may can use the forcereset version to "force" the issue.

Either of the "forcereset" files WILL reset the outlets.

From the menu, select Support.
If the settings are protected, reset the protection. 
Press the reset button near the RJ-45 Ethernet connector and wait about 5 seconds. 
You will hear a beep and arrive at the reset menu. You can use the Up/Down arrows to select the kind of reset. The default is "Clear Lock Bits: Clear protection bits only", which is what you want. Press the cycle button.







