The Sennheiser BA 40 is a rechargeable, Li-Ion battery pack designed for the Sennheiser SpeechLine Digital Wireless (DW) series of microphones, specifically the SL Tablestand DW and SL Boundary DW transmitters. Its features include a 2200 mAh capacity, a 3.6V output, and a lightweight design (approx. 70g) for seamless power and reliable performance, ensuring uninterrupted use for presentations and meetings. It offers flexible charging options, including USB charging and optional wireless charging, contributing to its overall convenience.