On the rear panel are RCA and XLR input jacks, two pairs of high-quality binding posts, an SD card slot for firmware updates, a master on/off switch, the IEC AC input, and two RJ45 jacks for MBL's SmartLink, to allow communication among system components. The C15's rated output power is 280W into 8 ohms or 480W into 4 ohms (footnote 2), and its gain can be switched between 20dB balanced, labeled "XLR" on the display; and 26dB balanced or single-ended, respectively indicated by the display as "XLR High" and "RCA."