Gerry,

TIS is entirely Mode S based. It uses Mode S as a source to identify the
traffic near you and Mode S datalink service to uplink the data to your
aircraft.


Uhm, not quite, AFAIK. It does use Mode S datalink for the uplink, but all
traffic information is derived from center radar data. Mode C and A targets
are reported just as Mode S targets are.

--
Thomas Borchert (EDDH)