A method of transmitting data between a transmitter and a receiver via two pairs of wires (310, 320) extending between the transmitter and receiver, the transmitter including first and second transmitter portions and the receiver including first and second receiver portions for receiving signals transmitted by the transmitter in a differential mode, the method comprising: transmitting, from the transmitter to the receiver, using a discrete multi-tone protocol capable of using a number of different tones, a data signal in which related signals are transmitted onto both pairs of wires (310, 320) in a differential mode, and each of the first and second receiver portions receives the signals, converts them into the frequency domain and then processes the resulting signals using frequency domain equalisation coefficients calculated in dependence upon estimated channel transfer functions associated with the direct differential mode channels between the corresponding transmitter portion and each respective receiver portion and additionally in dependence upon estimated channel transfer functions associated with the crosstalk channels between the other transmitter portion and each receiver portion; wherein after processing the received signals using the frequency domain equalisation coefficients, the resulting signals are combined to form a combined recovered signal which is further processed to obtain the transmitted data; and wherein the related signals are transmitted onto both pairs of wires (310, 320) in a differential mode in respect of only a first subset of the tones usable by the transmitter and the receiver and wherein unrelated signals are transmitted onto the two pairs of wires, for each tone in a second subset of the tones usable by the transmitter and receiver, wherein the unrelated signals are vector precoded before being transmitted onto the wires and characterised in that a cut-off frequency and/or tone demarcates between the first and the second subsets such that tones in the first subset are associated with frequencies above the cut-off frequency and/or tone and tones in the second subset are associated with frequencies up to and/or below the cut-off frequency and/or tone, wherein the selection of the cut-off frequency and/or tone to be used is based on an assessment of the viability of sending data in vectored modes over the tones in the first and/or second subsets. transmitting, from the transmitter to the receiver, using a discrete multi-tone protocol capable of using a number of different tones, a data signal in which related signals are transmitted onto both pairs of wires (310, 320) in a differential mode, and each of the first and second receiver portions receives the signals, converts them into the frequency domain and then processes the resulting signals using frequency domain equalisation coefficients calculated in dependence upon estimated channel transfer functions associated with the direct differential mode channels between the corresponding transmitter portion and each respective receiver portion and additionally in dependence upon estimated channel transfer functions associated with the crosstalk channels between the other transmitter portion and each receiver portion; wherein after processing the received signals using the frequency domain equalisation coefficients, the resulting signals are combined to form a combined recovered signal which is further processed to obtain the transmitted data; and wherein the related signals are transmitted onto both pairs of wires (310, 320) in a differential mode in respect of only a first subset of the tones usable by the transmitter and the receiver and wherein unrelated signals are transmitted onto the two pairs of wires, for each tone in a second subset of the tones usable by the transmitter and receiver, wherein the unrelated signals are vector precoded before being transmitted onto the wires and characterised in that a cut-off frequency and/or tone demarcates between the first and the second subsets such that tones in the first subset are associated with frequencies above the cut-off frequency and/or tone and tones in the second subset are associated with frequencies up to and/or below the cut-off frequency and/or tone, wherein the selection of the cut-off frequency and/or tone to be used is based on an assessment of the viability of sending data in vectored modes over the tones in the first and/or second subsets.