The present external source of input power. The enumeration 'none(2)' indicates that there is no external source of power, for example, the UPS is On Battery (an internal source). 'primaryUtility' indicates the normal case of utility input power. The 'bypassFeed' can only be used when the Bypass source is known to be a separate utility feed than the primaryUtility(3). 'secondaryUtility' indicates that a secondary utility feed is supplying power (on a dual AC input UPS). 'generator' indicates that input power is provided by a generator. Note that the alternate energy sources of 'flywheel' and 'fuelcell' are not necessarily AC input sources.