Abstract: Apparatus for measuring the distance between an electric welding torch and a workpiece especially useful with an aluminum workpiece. A nonconsumable electrode is mounted adjacent the consumable electrode of the welding torch with the nonconsumable electrode electrically isolated from the consumable electrode. A power supply connected to the consumable electrode provides an auxiliary arc and develops a consumable electrode voltage proportional to the distance between the torch and the workpiece. The consumable electrode voltage can be used to develop signals which guide the torch along a groove in the workpiece.

Abstract: A process for the prevention of the propagation of errors in a security processor having processing circuits which carry out arithmetic and logic operations on given operands, and detection devices for detecting single definite breakdowns occurring in these processing circuits in which single ambiguous breakdowns resulting in the weakening of a signal are detected by the detection of the single definite breakdowns, by using signal interpreting circuits which make the weakened signals definite, whether or not correct. In addition, definite or ambiguous breakdowns of these interpreting circuits are also detected by the detection devices.