The PN3C has a fixed and calibrated output level of -26 dBV. Its low output impedance allows it to drive both high and low input impedances without going out of regulation. It has a regulated and filtered power supply which can be supplied by an external AC adapter or a 9V battery. A power status Led indicates when lit that the battery is supplying adequate power. The PN3C turns on when a 1/4 inch phone plug is inserted in the output jack. There are no external controls.