There is no dedicated SX-50 forum... Sorry... The SX-50 has been discontinued for well over 10 years and with the life an average digital phone system being 7-10 years... well, you get the idea, even though the SX-50 has an excellent life cycle, few issues arise with this system anymore to dictate a dedicated forum area.
That being said, many of us here are long time Mitel users and this section is as close as you are going to get...
Register 185 is for the Attendant Console Key assignments, you are only allowed registers 1-14 (ie. key number), there is no higher register that I am aware of because the console does not have that many keys.
