LtDoc

This is a common problem with any proprietary system of any kind. It doesn't necessarily follow any particular 'standard' scheme except for the manufacturer's. Keeps 'others' from using -their- system for a cheaper radio, sort of.
There are two solutions, change to a 'standard' system, or find out exactly how 'their' system works and make it work. Both have disadvantages, time and learning, or money. Take your pick. There ain't no 'free lunches', but sometimes the 'price' is sort of variable... kind of.
Good luck.
- 'Doc


(If you can get 'them' to tell you exactly how 'their' system works, and it does, count your self 'blessed' to have been present during a "miracle"! Most manufacturers ain't gonna tell you...)