RGN_Tool is NOT used directly with your device and nor can it detect a device in any way. It is strictly a firmware manipulation tool designed solely to view, save or replace various components [*.bin files] of a firmware file [*.rgn or *.gcd]. In this thread it's being used solely for extracting the firmware's boot.bin [Ldr.bin] to use in executing the txt command to save region 41 or 154 as a bin file [in your nuvi 2689 it's the latter region number, saved to '2' for the microSD path].

Read the tut in Post #1 carefully again. Best you do it yourself but if you're still totally confused one of us will make you a kit suitable for your HWID of 1948.