For battery operation, {HEAD ~ the power circuit} can include an inverter for converting direct current power to {TAIL ~ alternating current power}, and a selectively adjustable frequency regulator for regulating the discharge current frequency 
For battery operation , { HEAD ~ the power circuit } can include an inverter for converting direct current power to { TAIL ~ alternating current power } , and a selectively adjustable frequency regulator for regulating the discharge current frequency
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH