In a communications system, a momentary loss of signal. Note: Dropouts are usually caused by noise, propagation anomalies, or system malfunctions. 2. A failure to read properly a binary character from data storage. Note: A dropout is usually caused by a defect in the storage medium or by a malfunction of the read mechanism. 3. In magnetic tape, disk, card, or drum systems, a recorded signal with an amplitude less than a predetermined percentage of a reference signal.