the insulation on the one hand of the three wires 12 13 14 thanks to the positioning of lower points to penetrate through the longitudinal axis of grooves 9 10 11 and wires 12 13 14 and on the other hand penetration of the three respective conjugate wires of the cable 1 thanks to the corresponding upper points fig4 6 show how in accordance with one of the multiple possibilities of implementation of the invention the end previously stripped of its outer sheath of the cable 4 is positioned fig4 then fig5 and 6 how the plate 8 is introduced by force in the lower box 6 which causes the conical points 32 33 34 to penetrate in the respective wrapped wires 12 13 14 these points then being electrically connected to these wires this first action may be carried out either in the workshop or on the site which in that case enables the cable 4 to be cut exactly to the required length at this stage the lower part of the connection device 2 of the invention is ready to be installed in situ and connected to the chosen point on the conductor cable 1 such connection in situ is effected as follows cf fig7 to 10 in this respect the upper half box 7 is firstly fig7 positively placed in position thanks to its guide members 28 30 mentioned above fig2 astride the conductor cable 1 then still according to fig7 the half box 6 fitted according to fig6 with the cable 4 is turned through 90 u00b0 in the direct sense in.