parallel thought line.
I had wondered why no one produced a solid state stand alone ADSB transponder that could be fitted to an aircraft with not much beyond a radio in the way of electronics.
CASA in their infinitesimal wisdom have made it illegal.
the reasoning being that the adsb info must never be different to the information presented to the pilot.
....but what if there is NO information being presented to the pilot?
their logic, or lack of it, beggars belief at times.