Signalling system

A method of modifying a signaling system comprising a first data signal source and a first data signal receiver and at least two wire pairs, one of the at least two wire pairs coupling the first data signal source to the first data signal receiver,

• the method comprising:
• providing a magnetic core arrangement;
• winding a portion of each wire of the at least two wire pairs around the magnetic core arrangement;
• providing one or more further windings around the magnetic core arrangement;
• and
• providing a further signal source coupled to the one or more further windings, wherein the one or more further windings and the wires of the at least two wire pairs are electrically isolated from each other, and
• wherein the windings are arranged so the further signal source generates a common mode signal in each of the at least two wire pairs, and wherein the signaling system further comprises a second data signal receiver coupled to receive the common mode signal by a coupling arrangement which is coupled to one of the at least two wire pairs and coupled to the other of the at least two wire pairs to provide a return path for current induced in the at least two wire pairs by the one or more further windings.