The BP2 is actually 2 BP1s in the same enclosure. The A and B circuits operate independently of one another and may be used simultaneously. Only the headset amplifier is shared so that both circuits can be monitored on a single-muff headset. As you can see from the photograph, each circuit has its own volume control, signal button, signal lamp, mic on/off switch and sidetone control. The 2 circuits are connected to the rear panel XLRs so a Y-cable or SB1 Splitter Box is necessary for each circuit if you wish to loop through to the next station in that circuit.