A field-replaceable unit (FRU) is a

printed circuit board A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich str ...

, part, or assembly that can be quickly and easily removed from a computer or other piece of electronic equipment, and replaced by the user or a technician without having to send the entire product or system to a repair facility. FRUs allow a technician lacking in-depth product knowledge to isolate faults and replace faulty components. The granularity of FRUs in a system impacts

total cost of ownership Total cost of ownership (TCO) is a financial estimate intended to help buyers and owners determine the direct and indirect costs of a product or service. It is a management accounting concept that can be used in full cost accounting or even ecolo ...

and support, including the costs of stocking

spare part A spare part, spare, service part, repair part, or replacement part, is an interchangeable part that is kept in an inventory and used for the repair or refurbishment of defective equipment/units. Spare parts are an important feature of logist ...

s, where spares are deployed to meet repair time goals, how diagnostic tools are designed and implemented, levels of training for field personnel, whether end-users can do their own FRU replacement, etc.

Other equipment

FRUs are not strictly confined to computers but are also part of many high-end, lower-volume consumer and commercial products. For example, in military aviation, electronic components of

line-replaceable unit A line-replaceable unit (LRU), lower line-replaceable unit (LLRU), line-replaceable component (LRC), or line-replaceable item (LRI) is a modular component of an airplane, ship or spacecraft (or any other manufactured device) that is designed to b ...

s, typically known as

shop-replaceable unit A shop-replaceable unit (SRU) or shop-replaceable component (SRC) is a modular component of an airplane, ship or spacecraft that is designed to be replaced by a technician at a backshop. Repair at backshops is known as field-level maintenance ...

s (SRUs), are repaired at field-service

backshop A backshop or back-shop is a specialized store or workshop found in service industries, such as locomotive and aircraft repair. Most repairs are carried out in small workshops, except where an industrial service is needed. In the military, bac ...

s, usually by a "remove and replace" repair procedure, with specialized repair performed at centralized depot or by the

OEM An original equipment manufacturer (OEM) is generally perceived as a company that produces non-aftermarket parts and equipment that may be marketed by another manufacturer. It is a common industry term recognized and used by many professional or ...

History

Many

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type kn ...

computers had FRUs: * Pluggable units containing one or more

s and various

passive component Passivity is a property of engineering systems, most commonly encountered in analog electronics and control systems. Typically, analog designers use ''passivity'' to refer to incrementally passive components and systems, which are incapable of p ...

s Most

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...

ized and integrated circuit-based computers had FRUs: *

Computer module A computer module is a selection of independent electronic circuits packaged onto a circuit board to provide a basic function within a computer. An example might be an inverter or flip-flop, which would require two or more transistors and a s ...

s, circuit boards containing discrete transistors and various passive components. Examples: ** IBM SMS cards ** DEC System Building Blocks cards ** DEC Flip-Chip cards *Circuit boards containing monolithic ICs and/or hybrid ICs, such as IBM SLT cards. Vacuum tubes themselves are usually FRUs. For a short period starting in the late 1960s, some

television set A television set or television receiver, more commonly called the television, TV, TV set, telly, tele, or tube, is a device that combines a tuner, display, and loudspeakers, for the purpose of viewing and hearing television broadcasts, or using ...

manufacturers made solid-state televisions with FRUs instead of a single board attached to the chassis. However modern televisions put all the electronics on one large board to reduce manufacturing costs.

Trends

As the sophistication and complexity of multi-replaceable unit electronics in both commercial and consumer industries have increased, many design and manufacturing organizations have expanded the use of the FRU storage device. Storage is no longer limited to simply identification of the FRU itself, but now also comprises back-up copies of critical system information such as system serial numbers, MAC address and even security information. Some systems will fail to function at all without each FRU in the system being ratified at start-up. Today one cannot assume that the FRU storage device is only used to maintain the FRU ID of the part.

Notes

{{Reflist, refs= Newton, Harry: ''Newton's Telecom Dictionary'', 16th Edition, "FRU," p. 364. Electronic engineering Maintenance

Other equipment

History

Trends

See also

Notes