The old Scandinavian scheme, defined jointly by Televerket (now
Telia) and Ericsson. Gradually replaced by S12 and TIA/EIA-598,
but still turns up in legacy networks. Fiber position follows the
12-color sequence below — but tube color is not a
color cycle: tube 1 is red, tubes 2 and 7 are blue direction
markers, and every other tube in the layer is plain white. The
pattern restarts at tube 1 on each new physical layer. Note: on
higher fiber counts (13–24, 25–36...), a repeat that
lands on Black is left unmarked instead of ring-marked — for
Type E that's fiber 20, 32, and so on.