Goobay Cable splitter, Y-adapter, 2x CAT 5 Ethernet, shielded

The port doubler allows simply to lead two Ethernet lines via one CAT cable (cable sharing). This is possible because half of the wires in the network cable are not used. The port doubler does not require power, but it must always be used in pairs - one at each end of the cable. The first piece unites the signals on one cable, the second piece
separates them again on normal network sockets. However, this only works if you don't use Gigabit LAN and PoE. There, more wires are needed and the trick doesn't work.