The Crown PH-1A is a single channel phantom power supply unit. The power supply is capable of providing 17V phantom power while powered with two 9V alkaline batteries, or 24V phantom while powered with an external AC/DC power supply unit (PS-24 power supply not included). The unit features standard 3-pin XLR type input and output connectors. The PH-1A features sufficient hum filtering for extremely quiet operation, and transformer isolation further minimizes noise caused by bad grounding.