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