In electronics

Electronics

Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

 and particularly computing

Computing

Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...

, a jumper is a short length of conductor used to close a break in or bypass part of an electrical circuit. Jumpers are typically used to set up or adjust printed circuit board

Printed circuit board

A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

s, such as the motherboard

Motherboard

In personal computers, a motherboard is the central printed circuit board in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple...

s of computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

s.

Description

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 and ofch contact in a jumper block terminates in a small metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 pin. An appropriately sized conductive sleeve called a jumper, or more technically, a jumper shunt

Shunt

Shunt may refer to:* Shunt - a hole or passage allowing fluid to move from one part of the body to another* Shunt - a device allowing electrical current to pass around a point in a circuit...

, is slipped over the pins to complete the circuit.

Jumpers must be electrically conductive; they are usually encased in a non-conductive block of plastic

Plastic

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

 for convenience. This also avoids the risk that an unshielded jumper will accidentally short

Short circuit

A short circuit in an electrical circuit that allows a current to travel along an unintended path, often where essentially no electrical impedance is encountered....

 out something critical (particularly if it is dropped on a live circuit).

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

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

 speed and voltage

Voltage

Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...

 settings were often made by setting jumpers. Informally, technicians often call setting jumpers "strapping". To adjust the SCSI

SCSI

Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...

 ID jumpers on a hard drive, for example, is to "strap it up".

Jumper blocks and jumpers are also often used on motherboards to clear the CMOS

CMOS

Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...

 information, resetting the BIOS

BIOS

In IBM PC compatible computers, the basic input/output system , also known as the System BIOS or ROM BIOS , is a de facto standard defining a firmware interface....

 configuration settings. This allows the computer to boot if a recent BIOS setting made it unable to boot, or if the CMOS boot password

Password

A password is a secret word or string of characters that is used for authentication, to prove identity or gain access to a resource . The password should be kept secret from those not allowed access....

 was forgotten.

Move to reduce jumpers

Early generations of any given computer hardware

Computer hardware

Personal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...

 technology usually have many jumper blocks, often laid out in a way that is poorly documented and difficult to set correctly. Often, designers find ways to streamline and simplify the jumper layout. For example, a typical early model Intel 386 motherboard might have 30 or 40 jumper pairs, while the last production models typically had just a handful, or sometimes only one. Typically, each jumper block is assigned and labeled with a number, which is documented in an instructional list printed on the motherboard or in the manual.

The recent trend has been to try to eliminate jumpers entirely from hardware devices by the use of auto-configuration

Auto-configuration

Auto-configuration is the automatic configuration of devices without manual intervention, without any need for software configuration programs or jumpers. Ideally, auto-configuring devices should just "plug and play"...

 or software-controlled configuration. Configurations may be stored in NVRAM

NVRAM

Non-volatile random-access memory is random-access memory that retains its information when power is turned off, which is described technically as being non-volatile...

, loaded by a host processor, or negotiated at system initialization time. In some cases, hot swappable

Plug-and-play

In computing, plug and play is a term used to describe the characteristic of a computer bus, or device specification, which facilitates the discovery of a hardware component in a system, without the need for physical device configuration, or user intervention in resolving resource conflicts.Plug...

 devices may be able to renegotiate their configuration while the system is running. 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. With newer PCs, the most common use of jumpers is in setting the operating mode for ATA

AT Attachment

Parallel ATA , originally ATA, is an interface standard for the connection of storage devices such as hard disks, solid-state drives, floppy drives, and optical disc drives in computers. The standard is maintained by X3/INCITS committee...

 drives (master, slave, or cable select).

Systems using boards with physical jumpers, on the other hand, tend to be configured correctly by end users as, in general, non-technical people are less willing to physically alter hardware settings than they are to experiment with settings from the keyboard

Computer keyboard

In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches...

. They also have the advantage that they usually only need to be set once; while firmware

Firmware

In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...

 settings can be easily lost or corrupted by a careless user, a virus

Computer virus

A computer virus is a computer program that can replicate itself and spread from one computer to another. The term "virus" is also commonly but erroneously used to refer to other types of malware, including but not limited to adware and spyware programs that do not have the reproductive ability...

, or a power failure, the only way to alter a correct jumper setting is to physically change it.

External links

• Jumper Settings Archive via the Wayback Machine