A steel cord for reinforcing a breaker or belt ply in a rubber tire having a core group and a sheath group. The core group consists of two to four core steel filaments with a first diameter dc and the sheath group consists of one to six sheath steel filaments with a second diameter ds. The ratio dc/ds of the first diameter dc to the second diameter ds ranges from 1.10 to 1.70. The two core steel filaments are untwisted or have a twisting step greater than 300 mm. The sheath group is twisted around the core group with a cord twisting step in a cord twisting direction. The ratio of the difference in residual torsions of the core group and the sheath group to the difference in saturation level between the core group and the sheath group ranges from 0.10 to 0.65, preferably from 0.10 to 0.60.

A twisting device (10) for twisting or stranding electrical or optical lines (12) to form a line bundle (13). The twisting device (10) comprises at least one first twisting head (15) and a clamping device (25). The first twisting head (15) and the clamping device (25) are spaced apart from each other. The twisting device (10) has at least one detecting device (30) for capturing information indicative of a lay length of the line bundle (13). The at least one detecting device (30) can be moved relative to the first twisting head (15) and the clamping device (25).