Basically just an software update, and then enable it. As for the Subscriber units, that depends on if they are TDMA capable or not. If they are, then a quick touch, OTAP or the like and they are good to go. If not, then they will need replaced etc... Around half to three quarters of the units on SAFE-T are TDMA capable radios at this point. But the changeover will not be a fast thing. The system will be set to use both FDMA, and TDMA at first, and for a few years will be that way. Then they will begin the final switch to TDMA ONLY.