The PMA-245H is a dual input, 18 volt, 45 watt, plenum rated stereo amplifier/mixer. It is ideal for above ceiling applications. The 5.43"W x 1.65"H x 4.8"D chassis dimensions allow three amplifiers to fit in one rack space. In addition, a uniquely designed heat-sink provides effective heat dissipation. The PMA-245H is intended for commercial and educational environments providing clear, crisp audio in a compact design. This new classroom audio system addition incorporates Roemtech's new Hummbuster Technology. This new technology is switchable allowing flexibility in resolving ground loop issues, should they arise.