An electrical cable consisting of pairs of conductors that have identical electrical characteristics with respect to each other and with respect to ground. The typical example in computer networking is the twisted-pair cabling used in 10BaseT Ethernet networks.
In a balanced line, both of the two wires are carrying current at any given instant. However, at any particular moment, the directions of the current in the wires are opposite each other. This condition is also described by saying that the currents in the wires are 180 degrees out of phase with each other at any given moment. Both wires have voltages that are above ground potential, but the potentials of the wires are different with respect to ground, resulting in a flow of current. The wire pair is twisted in order to ensure that the electromagnetic radiation produced by both wires is effectively canceled out, reducing the overall electromagnetic interference (EMI) produced by the wires and reducing their sensitivity to induced currents from external sources of EMI.
A balun can be used to connect a balanced line to an unbalanced line.