The AC power cord is necessary to be able to charge at home or anywhere with a standard wall outlet. This is strictly the AC power cord that plugs into the SeQual eQuinox power brick on one end, and a wall outlet with the other end. Before charging your eQuinox, make sure that the power cord is firmly attached to the power brick—when this is successful, a green indicator light will appear on the AC power supply and a plug icon will appear on the unit's control panel. This essential accessory ensures you can maintain your oxygen therapy and keep your batteries charged while at home or wherever a standard wall outlet is available. The cord operates on 85-264 VAC, 47 – 63 Hz.