cyril7: Like speaker cable, each conductor of the pair is in its own sheath and the two a molded together like a figure 8 as shown below.
Modern 2 pair is a single black sheath with the 4wires (in two pairs) inside, so it looks a bit like TV coax from the outside.
Thanks, but your link doesn't work.
From your description I think I recall that type of cable: it was twisted like a helix and came from the street telephone pole to the house. Am I correct?