Heritage Audio OST-4 V2, Empty Housing for up to Four 500 Series Modules, On Slot technology (power regulation for each individual slot), Link function (each channel can be linked to the next channel at the touch of a button), Power supply with 400 mA per rack, Phantom power supply (140 mA max. total demand), External power supply unit, XLR connections, Sheet steel housing with aluminium front panel, Design: 500 module series, 3U, Weight: 1 kg