This slide illustrates how bidirectional control channel works. The high-speed data is indicated in blue and the low-speed control, backchannel data is shown in orange. What is seen here is that the forward channel driver sends the high-speed data and the forward channel receiver, which is in the deserializer, receives that data at the same time. Then the backchannel driver sends the low-speed data from the deserializer across the same differential pair to the backchannel receiver. The key thing to note here is the continuous transmission of data in both directions over a single pair of wires. That means that both the forward channel driver and receiver are active at the same time that the backchannel driver and receiver are active.