| 摘要 |
A status indicator for monitoring a fuse or a circuit breaker, including optically isolated triggering and alarm circuits which can be integrated into a fuse holder or circuit breaker housing. More particularly, a status indicator having an LED connected in series with a fuse or circuit breaker across a power source, and a phototransistor arrangement, connected across the power source, in series with an alarm circuit. The arrangement is configured so that as long as current flows through the fuse or circuit breaker, the LED produces light which causes the phototransistor to be maintained in a non-conducting state, and the status indicator to remain in a non-alarm state. Upon failure of the fuse or circuit breaker, current flow to the LED is interrupted, resulting in the phototransistor being biased into a conductive state, and the alarm circuit being activated. A normally closed switch is employed to interrupt the current flow to the LED, thereby simulating fuse or circuit breaker failure, and providing a convenient manner for the on-line testing the status indicator. Multiple LEDs, each associated with a separate monitored fuse or circuit breaker, can be connected to a single normally closed switch, thereby facilitating the simultaneous testing of numerous status indicators through the actuation of a single switch.
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