the invention provides a gas - shielded arc welding system using two side - by - side electrodes each of which is provided with current pulses superimposed on a respective background current level to maintain the desired controlled spray transfer mode of the weld metal without overheating effects . the pulses are supplied to the two arcs out of phase with one another to minimize interaction of their magnetic fields , but this alone is not sufficient to assure stability of the two arcs . in the system of the invention , one arc is designated as the master arc and the other as the slave arc . the master arc is stabilized by means of a feedback loop controlling its master pulse frequency . each master pulse triggers a respective slave pulse after a preset time delay , in this way keeping corresponding master and slave pulses in synchronism . this is not necessarily sufficient to stabilize the slave arc and independent stabilization is therefore provided for it by a feedback loop controlling its pulse duration or its background current , but preferably by controlling both simultaneously .