Miller Electric created the Auto-Line input-power management technology and put it to work first in the ALT 304 CC/CV inverter to deal with fluctuating primary power, often called dirty power. Primary power voltage can vary, but as long as it stays within the machine's operating range of 190 to 630 volts, power at the arc remains steady. The ALT 304 uses a small inverter to convert primary power to a buss voltage, which drives the control part of the inverter. The machine—which performs very similarly to Miller's XMT 304 CC/CV—can plug into 208-volt or 575-volt primary power without any adjustments. Auto-Line even allows operation from straight DC power, such as from the third rail of a subway system. Estimated list price: $3,688 to $4,006.