Abstract: A socket including a casing having a number of partition plates formed on each lateral side of the socket a vertical receptacle and one or more lateral cylindrical chamber. A conducting plate is disposed in each receptacle bearing against a vertical partition plate. A protuberance set includes a cylinder, a ball and a spring both retained seriesly in the cylinder. A protuberance set is provided in each of the cylindrical chambers so that the ball slightly protrudes from the receptacle.