The first step in the selection process is to determine the AC voltage of the wall outlet that the surge suppressor will be connected to: either 120 V or 230 V nominal. "Nominal" refers to a standard range of closely-related voltages that the surge suppressor will accept. For example, although a surge suppressor is considered "120 V", it can be safely connected to an AC wall outlet that supplies any voltage between 110 V and 125 V.

