jumper

A jumper is a small metal bridge, typically made of tin-plated copper, that connects two pins on a printed circuit board or control panel. It completes a circuit path or selects between alternative configurations without requiring soldering or board modification. The metal connector sits on a pair of header pins spaced 0.1 inches (2.54 mm) apart, allowing it to be inserted and removed by hand.

In power distribution and utility equipment, jumpers are used to configure protection settings, select voltage ranges, or enable specific circuit branches. A substation control board might use jumpers to set the threshold at which an overcurrent relay trips, or to route signals between different protection zones. Because jumpers are non-destructive and reversible, technicians can change equipment behavior in the field without ordering new circuit boards or calling in specialized repair services.

Jumper configuration is documented on the board itself or in printed schematics provided with the equipment. The silkscreen label typically shows J1, J2, and so on, with adjacent text indicating what function each position controls. Open pins (no jumper installed) usually represent one state, while shorted pins represent another. Misplacing a jumper is a common source of field commissioning errors and mysterious equipment faults.

Physical variants and durability concerns

The basic jumper is a simple two-pin bridge; some designs include three or more pins to select between multiple states. The metal contact must resist corrosion and maintain low resistance over time; copper oxidation or loose insertion can create intermittent faults that are difficult to diagnose. In industrial environments with vibration or thermal cycling, jumpers can work loose and require periodic re-seating.

The term jumper likely derives from its function of jumping a connection across a gap. Though the technology is decades old and largely superseded by software-configurable electronics in modern equipment, jumpers remain common in legacy utility systems, protection relays, and devices designed for offline programming. They continue to appear in new equipment where simple, fail-safe field configuration is preferred over software menus and commissioning tools.