A device for the two-way inductive coupling of data signals to a low- or medium-voltage power line, comprising: - a ring-shaped magnetic core split into at least a first ring-shaped core segment and a second ring-shaped core segment articulated to one another, said ring-shaped magnetic core defining an opening for the arrangement therethrough of said power line, and each of said ring-shaped core segments (A, B) defining two end planar faces (11A, 12A, 11B, 12B) which define separating gaps and when they are opposite one another and when said ring-shaped core segments are surrounding said electric power line; - a connector for a coaxial cable for inputting and conducting said low-frequency data signal; and - a winding wound onto said ring-shaped magnetic core receiving said data signal from the connector and determining together with the power line a current transformer coupling said data signal between said power line and said winding through the ring-shaped magnetic core; characterized in that said ring-shaped magnetic core is made of a ferromagnetic material with the following properties: ∘ 1500 < ui < 150000 ∘ 1.2 T < Bsat < 1.6 T ∘ 4.8 uH < Al < 6 uH ∘ -1 < H < +1 (A/cm) where: ∘ ui is the initial magnetic permeability, ∘ Bsat is the magnetic saturation induction expressed in teslas, ∘ A1 is the inductance factor, and ∘ H is the magnetic excitation - said winding is formed by a copper sheet with two planar winding turns providing a 2:1 transformation ratio in relation to said power line; - electrical insulation is arranged between said copper sheet and the ring-shaped magnetic core; - said opposite planar faces (11A, 11B, 12A, 12B) of the ring-shaped magnetic core segments (A, B) are cut with mirror finish polishing; and - the assembly of the ring-shaped magnetic core and the winding is surrounded by an overmolded thermoplastic shell with a dielectric strength of 190 Kv/cm; such that the device is configured for operating with low-frequency data signals between 50 kHz and 600 kHz with attenuation of 8 to 10 dB in a 100 to 250 kHz band and of 4 to 6 dB in a 250 to 600 kHz band. - a ring-shaped magnetic core split into at least a first ring-shaped core segment and a second ring-shaped core segment articulated to one another, said ring-shaped magnetic core defining an opening for the arrangement therethrough of said power line, and each of said ring-shaped core segments (A, B) defining two end planar faces (11A, 12A, 11B, 12B) which define separating gaps and when they are opposite one another and when said ring-shaped core segments are surrounding said electric power line; - a connector for a coaxial cable for inputting and conducting said low-frequency data signal; and - a winding wound onto said ring-shaped magnetic core receiving said data signal from the connector and determining together with the power line a current transformer coupling said data signal between said power line and said winding through the ring-shaped magnetic core; characterized in that said ring-shaped magnetic core is made of a ferromagnetic material with the following properties: ∘ 1500 < ui < 150000 ∘ 1.2 T < Bsat < 1.6 T ∘ 4.8 uH < Al < 6 uH ∘ -1 < H < +1 (A/cm) where: ∘ ui is the initial magnetic permeability, ∘ Bsat is the magnetic saturation induction expressed in teslas, ∘ A1 is the inductance factor, and ∘ H is the magnetic excitation ∘ 1500 < ui < 150000 ∘ 1.2 T < Bsat < 1.6 T ∘ 4.8 uH < Al < 6 uH ∘ -1 < H < +1 (A/cm) ∘ ui is the initial magnetic permeability, ∘ Bsat is the magnetic saturation induction expressed in teslas, ∘ A1 is the inductance factor, and ∘ H is the magnetic excitation - said winding is formed by a copper sheet with two planar winding turns providing a 2:1 transformation ratio in relation to said power line; - electrical insulation is arranged between said copper sheet and the ring-shaped magnetic core; - said opposite planar faces (11A, 11B, 12A, 12B) of the ring-shaped magnetic core segments (A, B) are cut with mirror finish polishing; and - the assembly of the ring-shaped magnetic core and the winding is surrounded by an overmolded thermoplastic shell with a dielectric strength of 190 Kv/cm;