Field-replaceable unit
A field-replaceable unit is a printed circuit board, 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 and support, including the costs of stocking spare parts, 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 units, typically known as shop-replaceable units, are repaired at field-service backshops, usually by a "remove and replace" repair procedure, with specialized repair performed at centralized depot or by the OEM.History
Many vacuum tube computers had FRUs:- Pluggable units containing one or more vacuum tubes and various passive components
- Computer modules, 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.
For a short period starting in the late 1960s, some television set 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.