Lesson 4/Learning Event 2
through, which keeps it vibrating. Thus, the circuit breaker protects the battery from rapid
discharge when trouble develops. The circuit breaker will continue to vibrate until the trouble is
found and corrected.
In all types of circuit breakers, the short circuit must be removed before the breaker can be reset.
The short circuit can be located easily by disconnecting each circuit separately until the circuit
breaker stops vibrating.
Some automatic breakers do not vibrate, but have a telltale light placed across the contacts. This
light, generally placed where it is visible to the operator, is protected by a resistance. When the
circuit breaker contacts are opened by excessive current, the light flashes on. There is generally
sufficient current flowing through the relay coil with the lamp in series to hold the contact arm of
the circuit breaker down until the short is removed. After removing the short, it may be necessary
to turn off all lights for an instant to permit the relay to reset itself and extinguish the telltale light.
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