Abstract: An electrical connecting cable having a central coaxial unit around whose outer conductor a layer of conducting wire is placed. Several coaxial units identical to the central unit are wound around the layer of wires, the whole being surrounded by a sheath having an outer cover of an insulating material. Preferably, seven units are wound around the central unit.

Abstract: A bridge circuit comprising an isolation transformer having six primary windings which are connected so that the voice currents do and the supply currents do not generate, for either direction of current flow, a resulting flux in the core of the transformer. The bridge comprises two transistor circuits which prevent the voice currents from flowing through a supply source connected to the bridge and also balance the bridge circuit so that the influence of longitudinal noise signals which are produced in a transmission line connected to the bridge circuit are suppressed. The direction of the feed current in the transmission line can be reversed by means of the transistor circuits.