Oh, this is damn cool. 10Base-T1S. 10Mbit standard ethernet (including POE) over a single twisted pair that's daisy chainable. There's a guy making ESP32 board with it on (https://www.crowdsupply.com/silicognition/mant1s). Also, check apalrd's video on them: https://www.youtube.com/watch?v=5FBE-rjFLSQ