Apparatus and methods for transmitting digital video data and auxiliary data over a four twisted wire pair cable, and systems using such apparatus, are described. A first, second and third digital video color signal and a digital video timing signal are transmitted using differential mode signalling over a first, second, third and fourth twisted wire pair of a cable. Auxiliary data is sent over a data channel using common mode signalling over a first pair of the four twisted wire pairs of the cable. A common mode choke can be used to add or remove a signal sent using the common mode signalling from a pair of wires also used to transmit one of the digital video color or digital video timing signals.