Originally Posted by
magpienja
Can a controller get an instant response on VHF voice I wonder if he needs to...or is the a/c VHF muted like HF till its woken up by selcal?
Yes, on VHF it's headsets on and listening watch. The use CPDLC helps to keep routine stuff like frequency changes off the radio, freeing up space for more important instructions. A lot of controllers use it that way.