Quickly Alerting Personnel to a Blown Fuse is of Great Value

Time is often wasted before a blown fuse is detected and replaced. This is particularly true in prototype debugging, since the engineer may feel that his unproved design, rather than an accidentally blown fuse, is causing the problem. In unattended equipment such as component life-test racks and process-control systems, a positive means of quickly alerting personnel to a blown fuse is of great value. Fuse holders with neon indicators, though useful, do not adequately satisfy this need, since their signal may not be observed quickly enough.

An audible alarm wired across all system fuses, as shown in the figure, will be activated whenever a fuse blows. The alarm can be one of the small panel-mounting piezoelectric units available through electronic distributors. Diodes are required for isolation when more than one fuse is being monitored, but they also permit the use of alarms that require DC for proper operation.