The present invention teaches a communications system comprising a first communications device for receiving data and a wake up signal. The first communications device comprises an active mode of operation and a sleep mode of operation for reducing power consumption. Further, the system comprises means for switching the first communications device to and from sleep mode in response to receiving the wake up signal. Further, the system comprises a second communications device for transmitting data to the first device during its active mode, while transmitting the wake up signal to the first device during its sleep mode.