This bias tee box is used to insert AC or DC power into an HF signal to power remote antenna preamplifiers (DC), Bi-directional beverages (AC) or other devices. It is usually positioned at the receiving end of the coaxial cable to pass AC or DC power from an external source to the coaxial cable running to powered device. A bias tee consists of a feed inductor to deliver AC/DC to a connector on the device side and a blocking capacitor to keep power supply from passing through to the receiver. Bias tees are used in a variety of applications, but are generally used to provide an RF signal and power to a remote device where running two separate cables would not be advantageous. This box offers something more like: protections, variable attenuator and input common-mode filter.
Providing an RF signal and (AC or DC) power to a remote device over one coax
You can use bias tee BOX on both sides as power IN and OUT from RF coax