adsl ADSL Filter Peculiarity

[redoaklettuce]

Hi all, 

So I live in Australia, and I don’t yet have nbn (what a surprise). I’m still on an ADSL connection, and we recently moved houses and got a new modem. While connecting and testing the network, I had a quick look at the splitter/filter that plugs into the wall outlet. As it turns out, the in/out ports on the splitter are pretty weird, at least to me. They fit an RJ45 connector, but they only have 4 contacts in the port (Is 8P4C a thing?). But, RJ11 connectors are used for phone lines and ADSL connections. So telstra have little plastic inserts that convert the RJ45 into an RJ11. What is the point of all this conversion even though there’s only 4 contacts in the port!?

[mynameisjuan]

Cat3. Same RJ45 but only 4 pins for 100 meg