This is my first time here, and if this isn't the right place for this question, my apologies. Please direct me to the right place.
In order to get a wired LAN connection to a desktop computer and a printer using the one Ethernet jack available in that room (due to home wiring), I am interested in "splitting" the RJ45's cable into two different "lines" using this splitter on Amazon. Many people (and apparently the maker of this adapter) seem to believe you can functionally use only 4 wires inside a RJ45 cable to sustain a reliable LAN connection, which would allow you to use one RJ45 cable to be used as "two" cables using this adapter. My understanding is you use two Ethernet patch cables to go from two ports on a router into this adapter which uses 4 wires of the 8 wire total RJ45 cable for each connection, and then put the same adapter on the other end of the line and "split" the signals back out into two RJ45 jacks on the adapter so two Ethernet devices can plug in.
Or at least that's what I think.
First off, is my idealism valid, or is this actually nothing but a signal combiner? Can you indeed establish an Ethernet LAN connection using 4 wires of a RJ45 cable instead of 8?
Secondly, if this is possible, how much network performance would the devices lose due to less copper as compared to a dedicated Ethernet cable? In my case, I am running a 50' run, which (I think) is a decent amount of cable, but isn't a stretch to the 100 meter standard.