释义
n.
a mechanism in a clock or watch that alternately checks and releases the train by a fixed amount and transmits a periodic impulse from the spring or weight to the balance wheel or pendulum
（钟表的）擒纵机构。
a mechanism in a typewriter that shifts the carriage a small fixed amount to the left after a key is pressed and released
（打字机上控制行距的）棘轮装置。
the part of the mechanism in a piano that enables the hammer to fall back as soon as it has struck the string
（钢琴上使音锤击弦后立即复位的）控键装置。
词源
"late 18th cent.: from French