The Sennheiser AB 4-BW (article 508541) is a filtered, in-line UHF antenna booster module with BNC connectors, designed to add typically 12 dB of gain to make up for signal loss on long antenna cable runs between remote antennas and wireless receivers or an antenna splitter. It is fully compatible with legacy Sennheiser evolution wireless systems, and its filters have been widened to cover bandwidths of up to 88 MHz. This BW version covers 626 - 698 MHz, so it must be matched to receivers and antennas in the same frequency range; confirm that the range is appropriate for your region's regulations. It is 50 ohm, draws its power from the receiver or splitter via the antenna cable (DC feed), and weighs about 130 g, measuring approximately 95 x 47 x 21 mm. Typical users are rental companies, churches and venues running evolution wireless racks.