in the fixed standard 4 a saddle 20 arranged along the center line of the support 2 permits the passage of a spring 22 acting resiliently between the fixed standard 4 and an assembly of movable contacts 24 of the relay 10 a further pair of recesses 26 and 28 arranged forwardly of the recesses 12 and 14 in the support 12 constitute seat and guide elements for the passage of a pair of conductor wires 30 32 for feeding the printed circuit 6 a pair of projections 34 and 36 arranged parallel to each other and following the outer profile of the saddle 20 define a guide for the passage of the conductor 32 for feeding the signaling device the printed circuit 6 is accommodated on a plane surface 15 of the support 2 and adhesively connected thereto fig2 and 3 show the printed circuit 6 and the equivalent electric circuit respectively for greater clearness the latter has been connected to a coil 40 generating the magnetic field of the relay 10 the printed circuit 6 shown in fig2 comprises a base 38 of insulating material a led 44 and a resistor 46 connected in series to the led 44 the latter two components constitute the light signaling assembly when the relay is energized the resistor 46 is made by depositing on the printed circuit 6 a light layer of highly resistant.