Coupling circuit (100; 700; 800) for power line communications between electrical devices (50, 20, 30) connected to an electric network having a first, a second and a third phase line and a neutral line, comprising: - a first, a second and a third conductor each connectable to one of aforesaid electric phase lines (U, V, W) of the electric network and a fourth conductor connectable to the neutral line; - at least one input port (1U-1N, 1N-1V, 1W-1N, 1U-1V, 1V-1W, 1W-1U) proximal to an input portion of coupling circuit formed by any two of said first, second, third and fourth conductor for receiving a differential input signal to be transmitted on the electric network; - a plurality of output ports (2U-2N, 2N-2V, 2W-2N, 2U-2V, 2V-2W, 2W-2U) proximal to an output portion of the coupling circuit, each output port being formed by any two of said first, second, third and fourth conductor; - a transformation circuit block (10; 70; 80) of the differential input signal to make available differential output signals (S2, S3, S4, S2', S3', S4') on each of said output ports (2U-2N, 2N-2V, 2W-2N, 2U-2V, 2V-2W, 2W-2U) of the plurality of output ports, said transformation circuit block (10; 70; 80) being interposed between the input portion and the output portion of the coupling circuit and comprising: - a first winding (11; 11a; 11b) having a first terminal (1; 1a; 1b) connected to the first conductor through a first circuit filtering block (C1, L1) and a second terminal (2; 2a; 2b); - a second winding (12; 12a; 12b) having a third terminal (3; 3a; 3b) connected to the second conductor through a second filtering circuit block (C2, L2) and a fourth terminal, wherein said fourth terminal is connected to the second terminal of the first winding; - a third winding (13; 13a; 13b) having a fifth terminal (5; 5a; 5b) connected to the third conductor through a third filtering circuit block (C3, L3) and a sixth terminal (6; 6a; 6b) operatively connected to the fourth conductor, wherein the second terminal (2; 2a; 2b) of the first winding is operatively connected to the third conductor or to the fourth conductor. - a first, a second and a third conductor each connectable to one of aforesaid electric phase lines (U, V, W) of the electric network and a fourth conductor connectable to the neutral line; - at least one input port (1U-1N, 1N-1V, 1W-1N, 1U-1V, 1V-1W, 1W-1U) proximal to an input portion of coupling circuit formed by any two of said first, second, third and fourth conductor for receiving a differential input signal to be transmitted on the electric network; - a plurality of output ports (2U-2N, 2N-2V, 2W-2N, 2U-2V, 2V-2W, 2W-2U) proximal to an output portion of the coupling circuit, each output port being formed by any two of said first, second, third and fourth conductor; - a transformation circuit block (10; 70; 80) of the differential input signal to make available differential output signals (S2, S3, S4, S2', S3', S4') on each of said output ports (2U-2N, 2N-2V, 2W-2N, 2U-2V, 2V-2W, 2W-2U) of the plurality of output ports, said transformation circuit block (10; 70; 80) being interposed between the input portion and the output portion of the coupling circuit and comprising: - a first winding (11; 11a; 11b) having a first terminal (1; 1a; 1b) connected to the first conductor through a first circuit filtering block (C1, L1) and a second terminal (2; 2a; 2b); - a second winding (12; 12a; 12b) having a third terminal (3; 3a; 3b) connected to the second conductor through a second filtering circuit block (C2, L2) and a fourth terminal, wherein said fourth terminal is connected to the second terminal of the first winding; - a third winding (13; 13a; 13b) having a fifth terminal (5; 5a; 5b) connected to the third conductor through a third filtering circuit block (C3, L3) and a sixth terminal (6; 6a; 6b) operatively connected to the fourth conductor, wherein the second terminal (2; 2a; 2b) of the first winding is operatively connected to the third conductor or to the fourth conductor. - a first winding (11; 11a; 11b) having a first terminal (1; 1a; 1b) connected to the first conductor through a first circuit filtering block (C1, L1) and a second terminal (2; 2a; 2b); - a second winding (12; 12a; 12b) having a third terminal (3; 3a; 3b) connected to the second conductor through a second filtering circuit block (C2, L2) and a fourth terminal, wherein said fourth terminal is connected to the second terminal of the first winding; - a third winding (13; 13a; 13b) having a fifth terminal (5; 5a; 5b) connected to the third conductor through a third filtering circuit block (C3, L3) and a sixth terminal (6; 6a; 6b) operatively connected to the fourth conductor, wherein the second terminal (2; 2a; 2b) of the first winding is operatively connected to the third conductor or to the fourth conductor.