PURPOSE: To conduct electricity to a wire by operating an arc starter and to prevent elctric shock accidents by misoperation by closing the switch of a welding torch then opening the same and a gain closing it.

CONSTITUTION: When a switch 12 is closed, relays 14, 19 are closed, and other relays 15, 16, 17, 18 and 22 are opened. Here, when the switch 12 is opened, the relay 14 is opened but the relay 19 requires a time until it opens owing to the effect of a capacitor 20. After a few seconds, the relay 19 is opened and no high frequencies are generated and no wire is fed despite reclosing of the switch 12. Hence, the relay 22 is held closed as well while the relay 14 is opened and the relay 19 is held closed. It is not until the reclosing of the switch 12 that high frequency voltage is generated between the output terminals of a welding machine, and this makes it possible for the operator to be always aware that the devices are different.