The latest version of DERT that is out that I know of loads HFA V3 R0.18.0 onto the phone - I'm not quite sure if you are referring to the version of DERT software or the version of firmware it goes to put on the phone. If you look in the FAQ here, or another post that talks about software downloads and look up the Tonido site we use here for file transfer you can download the latest version. I look on occasion but haven't found anything newer, but I will say I don't know why they stopped with V3 R0.18.0 because that software version has issues and once I recover the phone I immediately push out something newer than that to the phone. There is a Readme file that comes with DERT - you have to follow those instructions - the laptop/pc network port needs to be configured to a specific IP address that the phone looks for to netboot, and you have to enable the DHCP and TFTP in DERT, which is why I have a dedicated laptop for this purpose that is not connected to our network, as I'm afraid there might be a few computers that just happen to boot up while that DHCP server is running and give the IT people a bad day! You can use a crossover network cable between the laptop and phone, or you can plug the laptop and phone into a little network hub and use an optiset / openstage power subbly to power up the phone. I use a crossover network cable and a POE power injector for a direct connection between the laptop and the phone.
I should point out there is also a SIP version of DERT, if that is your preference, but I don't know why anyone would want to downgrade the feature set on their phone if they are running them on a 4000.
Don Bruechert, Voice Comm Analyst II
CareTech Solutions @ Holy Family Memorial
Manitowoc, WI, USA