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