Not give the RAS in the first place, oops wrong thread
Squalk saturation plays a little part too, so if an appropriate ORCAM code isn't available, a domestic one is issued and will probably need changing by every new centre you talk to. Another problem is that if you are only in the first centres airspace for a short time, your code can be reissued quickly, which may then still be worn by the previous a/c inside a much larger FIR when you enter, hence new squalk needed.