A dropout is a momentary loss of signal in a communications system, usually caused by noise, propagation anomalies, or system malfunctions. For analog signals, a dropout is frequently gradual and partial, depending on the cause. For digital signals, dropouts are more pronounced, usually being sudden and complete, due to the cliff effect. In mobile telephony, a dropout of more than a few seconds will result in a dropped call.

•  This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22. (in support of MIL-STD-188).