Sony products are quite consistent across models about what signals are used for Discrete (and other) functions, though not consistent about which discretes exist at all.
There are lots of CCF files for Sony products here at RC. If you find a discrete for a similar model in some CCF, test it and it will probably work. If it doesn't work then test some basic function from the same CCF. If that does work than you can be nearly sure that your model lacks that specific discrete. If the basic function doesn't work either, pick a different "similar model".
The less experimental route is to use RHM's site to look up the command numbers of the discrete functions
[Link: anycities.com]then use my MakeHex program (or one of a few related tools) to generate clean Pronto Hex for the desired command numbers and test those (it still requires experiments, but with fewer unknowns involved, but2 it requires more understanding of the underlying principles vs. just trying commands from someone else's CCF).
