This Flarm splitter can be used in an installation where a Flarm is providing a GPS input to a standalone vario (such as the S8, S80, S10 and S100) and there is also a separate flarm display in the panel.
The splitter, with two types of output (RX/TX and TX only) it allows transmission between the vario and flarm unit, without transmitting to the flarm display (which should be connected to the TX only output).
Without this special splitter, you get a declaration error when you try to declare a task from vario to Flarm. This is because vario sends the declaration on the RX line in the RJ12 cable, which the alarm display pick up. This causes the declaration error because the declaration should only go to the Flarm unit, not to the display.