1. FOR APPLICATION TO A ROTATABLE SPEEDOMETER CABLE HAVING TWO ALIGNED SECTIONS, A COUPLING ASSEMBLY DRIVINGLY INTERCONNECTING THE CABLE SECTIONS, THE COUPLING ASSEMBLY COMPRISING, IN A SINGLE UNIT, A STATIONARY HOUSING CONCENTRIC WITH THE CABLE SECTIONS, AND A TWO-POSITION DWELLFREE SWITCH UNIT MOUNTED WITHIN THE HOUSING AND IN CONNECTION WITH ONE OF THE CABLE SECTIONS TO BE PERIODICALLY OPERATED THEREBY TO A MOMENTARILY CLOSED POSITION, THE SWITCH UNIT COMPRISING A TRAIN OF GREAR ADAPTED TO TRANSMIT MOTION FROM OEN OF THE CABLE SECTIONS TO THE TERMINAL GEAR IN THE TRAIN, TWO SPRING BLADES, EACH SUPPORTED AT ONE END, THE FIRST ON A FIXED MOUNTING WITHIN THE HOUSING AND THE SECOND ON THE TERMINAL GEAR TO BE CARRIED THEREBY THROUGH AN ORBITAL PATH INTO WHICH THE FREE END OF THE