Abstract: An information transmission method using arc and apparatus thereof are applied to a loudspeaker and the like having the function of illumination. The information transmission method is characterized in that arc current supplied to an arc generating device is modulated by a signal based on information to vibrate arc column so that at least one of audible waves, ultrasonic waves and arc light is employed to transmit the information. Arc having small mechanical inertia is employed as a sound producing device and accordingly can be used as a loudspeaker having a good frequency characteristic and large output. It can be used as a sound producing device having the function of illumination by utilizing strong light emitted from arc column.

Abstract: An automatic weld line following method for use with an arc welding method of welding a work by feeding a consumable electrode toward the weld line of the work through the tip of a welding torch and by oscillating the welding torch. The average and effective values of a welding current are detected, even if they are different, and fed to a computer so that the distance between the tip and the work is automatically controlled. At the same time, the oscillation angle is controlled to be symmetric at all times with respect to the weld line.