In electronic hardware, particularly computer systems, a field-replaceable unit (FRU) is a circuit board or part that can be quickly and easily removed and replaced by the user or by a technician without having to send the entire product or system to a repair facility. The defective unit is found by standard troubleshooting procedures, removed, and either discarded or shipped back to the factory for repair. The new unit is installed directly in place of the defective one.
The FRU scheme is often the most cost-effective way to maintain complex systems, and is a major motivating factor behind the evolution of modular construction. When backed up by good parts availability, knowledgeable technical support, and reader-friendly documentation, this approach can minimize system downtime and optimize reliability.