A method and apparatus for transmitting data from a transmitter device to one or more receiver devices connected to the transmitter device via a respective wire connection, the transmitter device being operable to transmit signals onto the wire connections and a further wire connection at different tones, the method comprising: for each tone, measuring electromagnetic coupling between the further wire connection and each of the wire connections and using the measurements, identifying a wire connection that most strongly receives crosstalk interference from the further wire connection; based on the identifications, for each tones, allocating signals transmitted on the further wire connection as supporting signals for a particular wire connection; transmitting a first signal onto the particular wire connection that has been allocated a supporting signal; and transmitting a second signal onto the further wire connection, thereby to cause crosstalk interference in the particular wire connection transmitting the first signal.