To unlock MMR (pedestr. features&Public transports)
otherwise in 37xx series the usual unlocking in normal CXs doesnt work-

edit: I add a further explanation coz seems it's not yet clear

37xx CXs are unlocked, but not unlocked in MMR section, so your gps can see the map, but you cant use pedestrian features and public transports if you dont add an .unl file made for FID 800- This FID has been altered by pop222-
MMR section contains these special features and are locked
Normal maps are good to unlock in ped and pubb. trans. just in other compatible devices like 12xx or 13xx eg. with FID and PID RegID you can find in normal CXs threads , in 37xx cant unlock special features it wont work, you need special FID 800 maps-
So if in 37xx you want to have public transports you need special FID 800 map and an additional .unl even if the map is unlocked-