There is provided a method of operating a communications system comprising a transmitting station and a receiving station, the method in the transmitting station comprising encoding a clock signal with data to form encoded signals for transmission; transmitting the encoded signals to the receiving station; the method in the receiving station comprising decoding the encoded signals to extract the clock signal and data; processing the data under the control of the decoded clock signal. The method further comprises, when no data is required to be transmitted to the receiving station, transmitting further encoded signals to the receiving station in order for the receiving station to decode the further encoded signals and extract a clock signal.