Sonifex CM-BH4WX Belt-Pack 4-Wire Headphone Amp with 4 Pin XLR Headset SocketThe CM BH4WX is a version of the CM BH4W with a 4 pin XLR headset connection instead of a stereo jack connector. In all other respects it is the same as the CM BH4W. Transformer Balanced I O The CM BH4W uses audio transformers at its input and output, providing galvanic isolation from outside interference, ensuring your communications are loud and clear, every time. 4 Wire And IFB Modes In 4 wire mode, the unit acts as a 2 way intercom, with input