Sound Link AL10, RCA/3.5mm over Cat5e/6, 2000ft.
Extend an audio signal from a 3.5mm or RCA port up to 2000ft away. Built-in switch allows for up to two inputs and two outputs, meaning you can connect two audio sources and switch between them to one of two different sets of speakers.
The Sound-Link also works to convert 3.5mm to RCA or the other way around. The connection type doesn't even need to be the same, it simply works all the time.
It is also bi-directional, so you can use either unit as a sender or receiver.