[计] 电路保护器; 断路器

[ noun ]
a device that trips like a switch and opens the circuit when overloaded
<noun.artifact>

circuit breaker \cir"cuit break"er\, n. (Elec.)
A device contained within an electrical circuit designed to
interrupt the circuit when the current exceeds a preset
value; it is sometimes called a {contact breaker}. Its
function is to prevent fire or damage to the circuit or the
devices on the circuit which could be caused by excess
current, such as that caused by a short-circuit. It differs
from a {fuse} in not having a conducting element which melts
(see 2nd {fuse}, n.). Circuit breakers are designed to be
easily reset, i. e. to reclose the circuit after it has been
opened by the circuit breaker; this is usually accomplished
by simply moving a switch back and forth. They are commonly
used in buildings to protect individual electrical lines, and
are often contained in groups within a box called a circuit
breaker panel, which divides the current from a main
electrical line into multiple circuits each protected by a
separate circuit breaker. Less commonly they may be found on
individual devices.
[PJC]