You can get ethernet to coax baluns and get 100Mbps and PoE. They're extremely reliable, passive (so little to break) and cheap. There might be gig versions n

You can get ethernet to coax baluns and get 100Mbps and PoE. They're extremely reliable, passive (so little to break) and cheap. There might be gig versions now. They're used to retrofit older surveillance camera wiring plants to ethernet without ripping out all the cables, but don't really care what type of ethernet device is on each end. If all you have is old phone wires in the wall, you can get a pair of xDSL (HVDSL) modems back to back and get up to 10Mbps or so. Better than nothing.