To upgrade a Protel v3 PBX to version 4, the disc drive must be wiped clean and a new server operating system installed on it.
Follow the preparatory instructions here
During your field upgrade session, a nexMatrix support technician will guide you through the complete process to install the new Linux OS onto the PBX server hard drive.
After the new Ubuntu 16.04 system has been installed, nexMatrix will need to be able to access your PBX via a remote SSH session (TCP port 22) to install the Protel LTS version 4 software. Your support technician can assist you with the necessary port-forwarding settings in your router.
The final steps after the updated software is installed will be to apply your backup configuration file. This will restore complete functionality to the PBX.
The entire process takes about 2 hours. Please schedule this with your account representative, or directly with nexMatrix support, at 855-639-6287.