The LISTEN Technologies LA-80 is a passive 2-way RF combiner. The LA-80 is a passive device, there's no power supply needed. The unit takes two 2 incoming RF signals and combines them into one 1 outgoing antenna source. In multiple channel applications you may need to use one antenna for multiple transmitters. This is sometimes easier than mounting multiple antennas due to space limitations or aesthetics. This combiner is used in applications where up to two 2 different antenna sources are required and only one 1 antenna output is available or desired.