foldback

Foldback is a term used in electronics, audio engineering, and related fields to describe mechanisms that feed back or revert signals to a prior stage, often for protection, monitoring, or control. Foldback current limiting is a protection method in power supplies and regulators whereby, on overload or short circuit, the output current is reduced and the output voltage collapses to a lower, safe level. This behavior contrasts with fixed-current limiting and helps inhibit overheating and allow safe recovery after fault removal.

In audio and live sound, foldback refers to the monitor feed—audio signals from the main mixer sent to on-stage monitors or in-ear monitors. It enables performers to hear themselves and the overall mix, and careful foldback management is important to minimize feedback and control stage volume. The term derives from the notion of folding the main mix back into the performers' monitoring path.

Other uses include diagnostic and protection schemes in instrumentation and telecommunications that employ similar feedback or level-reduction concepts to keep systems within safe operating limits. The concept embodies the principle of reintroducing control loops to maintain stability and prevent damage in complex systems.