BP1 belt packs are single-channel. The front panel controls are for the microphone, for controlling listening volume, and for signaling. The back panel has a 3-pin female XLR to connect to the system; a 3-pin male XLR for looping to the next station; a 4-pin male XLR for headset, and a switch to dynamic or electret.
BP2 belt packs are the same rugged construction as the BP1, with a second channel. Each channel may be signaled and volume-controlled individually. Separate mic buttons mean you may speak to either or both channels. Daisy-chaining BP2s requires a Y-cable, available at additional cost.