From Manufacturer
The AD 3700 Active Directional Antenna from Sennheiser features an integrated AB 3700 booster, and has a front-to-back ratio of >= 14 dB. It can supply up to 15 dB of amplification, and is compatible with the EM 3731, EM 3732-II, and EM 2000 wireless receivers. It's powered from the connected receiver, via its BNC input.