The SIEM-111 IEM System features reliable JTS UHF PLL technology.* There are 961 selectable UHF channels available. As many as 16 sets of SIEM-111T transmitters can operate on the same stage.* The system offers 4 groups, with each group having 16 compatible preset channels to choose from. This allows the monitor engineer to set up systems quickly and easily.* MPX Stereo Audio Transmission / Reception, switchable to Mono operation if desired.