The Sennheiser AB3-B is a filtered inline RF booster module. Designed to offer +10dB typical boost to compensate for signal losses created by long antenna cable runs. Essential for any professional wireless microphone set up or installation. The B band (626 – 668 MHz) filter removes all unwanted frequencies from reaching the receiver, allowing a better quality signal and performance. The AB 3 is fully compatible with all legacy evolution wireless systems.