reverse direction

In broadband transmission systems, a distinction is made between the signal flow directions from and to the central point, the head-end station. If the signal flow direction is from the terminal device to the head-end station, it is referred to as the backward direction or upstream; if it is from the head-end station to the terminal device, it is referred to as the forward direction or downstream. In single- cable broadband systems, different frequency ranges are used for the two transmission directions. Transmission in the backward direction is usually in the lower frequency range.