The illustration represents a current arrester, charge grounder, open-circuit alarm, and automatic live w ire tester, paten ted by Miller R. H utc hison, of No. 18 North Commerce Street, Mobile, Ala. It is intended to protect telegraph, telephone, fire alarm, call bell, and all low-potential inst ru m ents that are liable to dam age from lightni n g and live wires, giving n otice by an alarm bell of the passage of a heavy current, and de- term ining whether it is due to a stroke of lightning or a continuing and dangerous current from alive wire of high potential. The ordinary line current, entering the instrument at a binding post, passes by wire into ja ws on the base of the instrument, thence through a bar constituting a drag s wit ch and into a support, and through an u prig ht and wire to the metal hearing in which is j our n a l ed a s pring- actuated pivoted shunt bar, the limit of the motion of w h ich is indicated by the dotted lines. From the sh unt bar th e current passes to a pivoted armature lever normally held out of eon tac t with the magnet by a spiral spring, the bottom end of t h e magnet wire being also connected with the bearing in which the armature lever is journaled and the magnet being connected with a ground wire. When a live wire or heavy charge of lightning strikes the line wire, the magnet attracts the armature level- to free the shunt bar from its catch at the other end of the lever, when the shunt bar springs over to the position shown by the clotted lines, and into con-t act with spring jaws forming a sh unt bar support and h old er, a grounding wire from which grounds the charge and entirely cuts out the magnet. At the same time the rising of the a r m ature lever- effects contact, through a standard, with the terminals of a bell circuit to sound an alarm, the alarm bell ri n ging continuously until the in s tru m en t is reset. This may be effe ct ed by grasping a rubber handle of the shunt bar and pulling- it over until its end is caught by the catch of the armature lever but in case the alarm had been caused by a live wire, this would burn out the magnet before the armature lever could be a g ain removed from contact, and as a precaution against t his provision is made for opening the circuit automatically through the d r a g switch, the detail of which is shown in one of the small figures. With this switch in circuit there is no c urrent on the shunt bar w h e n reset by the operator, and not until the circuit is refor m ed by adjusting the drag switch, when, if the heavy current is still on, the shunt bar quickly and sensitively parts from the catch of the armature lever, and the magnet is not burned out. For switchboard use, or where more than one instrument is used, the instruments may be arranged on a table, as shown in one of the small figures. the connections being so made that the alarm will be rung from any one of the instruments.
This article was originally published with the title "A Lightning and Heavy Current Arrester"