Signal return

In unbalanced audio connections; one of the two signal conductors is typically at "ground" voltage potential. Because electrical signals can be both in the form of a voltage and a current; it is possible for a current to flow though a conductor that is at ground potential. For this reason; a coaxial cable's shield conductor can act as both a shield and a signal return.

It is also possible to use cable normally used for balanced connections to increase noise rejection of long unbalanced cables. This is sometimes referred to as a "quasi-balanced" connection. By using the "low" conductor of twisted-pair cable as the signal return; the shield can be disconnected at the receiving end to increase noise rejection.

For more information see adapter cable.