Jumper (computing)
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In
electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
and particularly
computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, ...
, a jumper is a short length of conductor used to close, open or bypass part of an electronic circuit. They are typically used to set up or configure printed circuit boards, such as the motherboards of computers. The process of setting a jumper is often called strapping. A strapping option is a hardware configuration setting usually sensed only during power-up or
bootstrapping In general, bootstrapping usually refers to a self-starting process that is supposed to continue or grow without external input. Etymology Tall boots may have a tab, loop or handle at the top known as a bootstrap, allowing one to use fingers ...
of a device (or even a single chip).


Design

Jumper pins (points to be connected by the jumper) are arranged in groups called ''jumper blocks'', each group having at least one pair of contact points. An appropriately sized conductive sleeve called a jumper, or more technically, a shunt jumper, is slipped over the pins to complete the circuit. A two-pin jumper only allows to choose between two Boolean states, whereas a three-pin jumper allows to select between three states. Jumpers must be electrically conducting; they are usually encased in a non-conductive block of
plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
for convenience. This also avoids the risk that an unshielded jumper will accidentally
short Short may refer to: Places * Short (crater), a lunar impact crater on the near side of the Moon * Short, Mississippi, an unincorporated community * Short, Oklahoma, a census-designated place People * Short (surname) * List of people known as ...
out something critical (particularly if it is dropped on a live circuit). Jumper shunts can be categorized by their pitch (uniform distance between pins measured from center to center). Some common pitches are: * * *


Use

When a jumper is placed over two or more jumper pins, an electrical connection is made between them, and the equipment is thus instructed to activate certain settings accordingly. For example, with older PC systems, CPU speed and
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...
settings were often made by setting jumpers. Some documentation may refer to setting the jumpers to on, off, closed, or open. When a jumper is on or covering at least two pins it is a closed jumper, when a jumper is off, is covering only one pin, or the pins have no jumper it is an open jumper. Jumperless designs have the advantage that they are usually fast and easy to set up, often require little technical knowledge, and can be adjusted without having physical access to the circuit board. With PCs, the most common use of jumpers is in setting the operating mode for ATA drives ( master, slave, or
cable select Parallel ATA (PATA), originally , also known as IDE, is a standard interface designed for IBM PC-compatible computers. It was first developed by Western Digital and Compaq in 1986 for compatible hard drives and CD or DVD drives. The connection ...
), though this use declined with the rise of SATA drives and
Plug and Play In computing, a plug and play (PnP) device or computer bus is one with a specification that facilitates the recognition of a hardware component in a system without the need for physical device configuration or user intervention in resolving resou ...
devices. Jumpers have been used since the beginning of printed circuit boards.


Permanent parts of a circuit

Some printed wiring assemblies, particularly those using single-layer circuit boards, include short lengths of wire soldered between pairs of points. These wires are called ''wire bridges'' or jumpers, but unlike jumpers used for configuration settings, they are intended to permanently connect the points in question. They are used to solve layout issues of the printed wiring, providing connections that would otherwise require awkward (or in some cases, impossible) routing of the conductive traces. In some cases a resistor of 0 ohms is used instead of a wire, as these may be installed by the same robotic assembly machines that install real resistors and other components. Jumpers setting configuration options not normally meant to be user-configurable can also be implemented as solder jumpers, typically two (or more) pads positioned closely together or even with interwoven shapes. Typically non-conductive by default they can be easily changed into a closed connection due to deliberately placed
solder bridge Solder mask, solder stop mask or solder resist is a thin lacquer-like layer of polymer that is usually applied to the copper traces of a printed circuit board (PCB) for protection against oxidation and to prevent solder bridges from forming b ...
on top of them. If the closed state is the default state, the PCB designer can superimpose a thin trace, which would be cut (with a knife) to open the jumper.


See also

*
DIP switch A DIP switch is a manual electric switch that is packaged with others in a group in a standard dual in-line package (DIP). The term may refer to each individual switch, or to the unit as a whole. This type of switch is designed to be used on a ...
*
Jump wire A jump wire (also known as jumper, jumper wire, DuPont wire) is an electrical wire, or group of them in a cable, with a connector or pin at each end (or sometimes without them – simply "tinned"), which is normally used to interconnect the ...
*
Pin header A pin header (or simply header) is a form of electrical connector. A male pin header consists of one or more rows of metal pins molded into a plastic base, often apart, though available in many spacings. Male pin headers are cost-effective du ...
*
Fuse Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protect ...
*
Busbar In electric power distribution, a busbar (also bus bar) is a metallic strip or bar, typically housed inside switchgear, panel boards, and busway enclosures for local high current power distribution. They are also used to connect high volt ...


References


External links

* {{webarchive , url=https://web.archive.org/web/20071011092722/http://th99.80x86.ru:80/ , date=2007-10-11 , title=Jumper Settings Archive Computer hardware tuning