Two combo inputs CH A (1-way XLR and Mono jack 6.35) are available in SA315, which can be switched between line input and microphone input. The audio port CH B(Mono jack 6.35 or a RCA port) is for the other sound resources like MP3, CD player, etc. There is 1-way signal input port for wireless bluetooth in it and the volume is controlled by terminal. The gain of CH A/CH B signal input is controlled by independent knob and 1-way master volume control knob. The four different audio sources can be parallel output with one-way XLR after mixed internally, and then sent to different speakers for sound distribution.SA315 can be installed by steel wire. It can also be standing by coupling bar or three-feet stand. The pole mount is 35mm. Various accessories are offered for SA315 to meet different kinds of installs.