The four channel F-M4SDI kit provides impressive density with a wide range of features. These units are the same size as the two channel systems, but provide double the video inputs. Just like all other Thor mini SDI transmitters and receivers, only one fiber is needed for all of the data. The four channel platform also features the versatile Aux port that can be ordered for a variety of applications. In addition to the return path RS-485 found on all Thor mini SDI systems, the Aux port provides an additional 5 pin terminal block that can be ordered for bi-directional or unidirectional audio, one or two independent RS-232/422 connections, or contact closure. The F-M4SDI fiber transport kit for HD-SDI, SD-SDI, or DVB-ASI comes with many standard features useful for video professionals. An optical link alarm (NOS) illuminates on both ends when a link cannot be established over the fiber. This immediately alerts operators on either the transmitter or receiver end of the link that there is a problem with the fiber. This system provides four fully independent SDI links over a single fiber cable at up to 1.5 Gbps each. In addition the Aux port can be configured to provide bi-directional stereo audio, dual RS-232/422 duplex connections, or up to 4 contact closure lines; all over a single strand of fiber.