Embodiments relate to a controller operable to transmit digital data messages to a receiver via a communication link having at least a first and a second transmission path, the controller comprising a first signal terminal the first transmission path and a second signal terminal for the second transmission path. The first signal terminal is operable to digitally transmit a first message to the receiver according to a first transmission technique and the second signal terminal is being operable to digitally transmit a second message to the receiver according to a second, different transmission technique.