With the increasing availability of Mode S transponders, and the cost coming down we are starting to see this technology already replacing current Mode C transponders, even in RA. We have 2 aircraft fitted with Mode S devices and strongly believe in the benefits of high level ( squitter) SSR interrogation and future ADSB out capability for traffic separation. It is important to note though that Mode S requires the assignment by CASA of a unique 8 or 16 digit hexidecimal address code that identifies the unit making it compliant,and that while GA issued Cof A's will include this number,to allow programming by the instrument LAME; RA registration does not necessarily do the same. I have posed this question to both RA-Aus and CASA's registration division as to how they will streamline this process with RAD47 compliance with the increasing rollout of Mode S units in RA-Aus. Still awaiting a reply.