Total posts : 45366
CAT3 phone cable has 2 twisted pairs. Use one pair for 12V power and the other for audio. Connect a 600 ohm transformer on one pair and with appropriate drive, you get excellent audio feed over long distances with no hum (no ground loops). I don’t know how far you can go, but I have tried 200ft and noticed no difference compared to 0ft.
Auto power adjust means there is circuitry that will maintain power input to the final stage so that 100mW is not exceeded.