No monitor can have SF3 "unlocked" 

Back in the day they had AutoTrac SF1 and AutoTrac SF2 for a $250 difference. First one was cheaper but could only steer SF1. Second one could steer any. 

Then a while back they figured out that wasn't a good idea and it's just one AutoTrac activation that steers anything. You must have 2630 or older? Either way, they'll either steer SF1 only or any signal. If you have an SF1 only, you can upgrade for $250 yet