The F-1MSDI-L-2TX is a mini Fiber Optic Transport unit that utilizes an extra loop out SDI connector, on the transmitter, for monitoring and for additional screening. The matching receiver F-1MSDI-L-2RX uses the same technology as the transmitter so you can acutally have 2 SDI outputs on the receiving end of the Fiber. This allows for easy access to redistribute a primary Fiber Cable that needs to be split to two SDI outputs.