a cell 23 form ground conductors 25 each differential pair of signal conductors 24 are flanked by ground conductors 25 the conductors 10 in the lead frame assemblies 17 18 are embedded in a casing 26 of an insulating material the cross section of fig2 shows the subassemblies 4 at a point where a recess 27 see fig4 b interrupts the insulating casing 26 uncovering lead portions 28 of the conductors 10 a t shaped sheet metal ground coupling bar 29 is inserted between the two subassemblies 4 in each cell 23 via the recesses 27 fig3 a shows an exemplary embodiment of such a ground coupling bar 29 the ground coupling bar 29 comprises a longitudinal main body 30 with a broadened head 31 on its top end the main body 30 comprises one side with three cut outs 32 having an inverse j shaped outline defining resilient fingers 33 which can be resiliently bent in a lateral direction at the opposite side the main body 30 is provided with similar cut outs 34 and resilient fingers 35 which are mirrored and arranged in a staggered manner relative to the cut outs 32 and fingers 33 of the first side of the main body 30 to reduce the contact surface between the resilient fingers 35 and the ground conductors 25 the free ends of the resilient fingers 35 are provided with a flattened or coined bulged.