Twisted in groups, insulated cores are systematized by groups in certain way and united in one common cable core.
There are homogeneous cores (with similar structure of elementary groups – quads, twains) and heterogeneous cores (with dissimilar twisting and elementary groups diameter).
According to the core formation character there are lay twisting and bunchy twisting. In the lay twisting elementary groups are placed around central group as concentric layers. Related lays are twisted in opposing sides for the purpose of cross-coupling decline and more mechanical strength for the cable core. Bunchy twisting means that groups were firstly united in bunches before they are twisted together.
For the stability of electrical characteristic and damp proofing of cable core, it is filled with waterbloking mass. The defence from the environment is realized by hermetic cover. Depending on the material there are metal (lead, aluminium, corrugated steel), plastic (polyethylene, polyvinyl chloride) and reinforced plastic.
Outer covering is placed over the cable covering. It protects the cable from mechanical damage. Because of mechanical effects on the cable during it’s laying and running there are two armor: a pair of steel stripe, a lay of round steel wire.
To protect cables from gnawing animals, they are covered with thin-walled one-layer strap (0.1 mm) in spirally way.
A special cable construction for stringing on airlines cable supports is foreseen. It includes in-built steel rope.
In follow articles will be shown basic specifications of cables elements, which are taken from a hand book with title “Urban Telephone Cables” (A.S. Brisker, A.D. Rug, D.L. Sharle, 1984). The reason of such an old source is that a lot of different cable constructions are used in telephone network, but the basic specifications of elements were saved.