Clovis, the terminology is still a bit tangled-up. "RCA" is the name of a plug on the end of many cables, not the name of a specific type of cable itself. An "analogue composite cable" is one use for a coaxial cable, not a separate and different type of cable.
I studied some of the stuff at the van den Hul site to see what the Thunderline was. After wading through some BS there, I saw that it was a two-conductor cable surrounded by a shield. If used with XLR connectors on the ends it could be a part of a balanced connection setup if the sending unit has a balanced output with two signals reversed in polarity with respect to each other and the receiving unit has a balanced input which combines the two signals(after putting them into same polarity). If RCA connectors are used, as you do, the result is essentially the same as a coaxial cable with one central conductor, except that two central conductors rather than one are carrying the identical signal. The comments in the previous reply regarding coaxial vs optic would still apply.
In googling van den Hul Thunderline I did run into one rather amusing comment on van den Hul done in
poetic form here .
