Test Leads with Sheet-Metal Spring Clips: Dusinberre, 1910

George Brown Dusinberre of Cleveland patented a testing clip for electric wires in 1910, US 963,425 (filed 1909). It is two sheet-metal members with crossed, serrated jaws, hinged on integral lugs at the back with no pivot pin. A U-shaped spring inside holds the jaws shut and is kept in place by flanges turned down at the sides. The upper member carries the sleeve that takes the wire. The jaws are serrated on the front edge and both sides, so a conductor can be gripped from any side, even in the crowded spaces of a switchboard. A length of insulated wire with a clip at each end makes a test lead.