The PMA-245 is a dual input, 18 volt, 45 watt, plenum rated stereo amplifier/mixer. It is ideal for above ceiling applications. The PMA-245 delivers a true 45 watts of power and will give even the largest classrooms the audio clarity needed. In many environments, ambient background noise such as HVAC systems and hallway traffic is an issue. With the PMA-245, these issues won't overpower your sound system.