The left speaker's back panel houses all of the connections, including the screw - on antenna for Bluetooth reception, the banana plug - style output that sends sound to the right speaker (a cable is included), an RCA - style stereo
input and output, a 3.5 mm audio
input for mobile devices, and a micro USB
input for connection to a computer — a way to bypass the digital - to -
analog converter on your speaker's output and
let the HD3 handle things.