In electric furnace systems, the electrode for supplying current to the furnace is normally moved up and down by a reciprocating mast mounted by upper and lower mast-guiding means fitting closely about the mast, the reciprocating motion being provided by suitable motor means. To prevent dangerous up-and-down extremes of travel of the mast, there is employed a normally-open type of switch means positioned between the upper and lower mastguiding means so as to be held closed by a surface of the mast during execution by the mast of its desired maximum length of travel. The mast surface is configured to permit the switch means to open when the mast moves beyond the desired maximum length of travel, and this opening of the switch is caused to deactuate the motor means. Preferably the configuring of the mast surface comprises providing a recess therein so positioned that when the switch arm, which normally rides along the exterior of the mast, reaches the recess, it moves into the recess to permit the switch to open and discontinue the motor operation. The position of the switch is preferably on the side of the mast away from the furnace means and within an at-least-partially protected region. Other arrangements employ more than one recess and/or switch, some of which may be used for normal arrest of the extreme motion of the mast and others of which may be used as back-up safety devices in case the normal mast-arresting arrangement does not function.