off-hook signal 摘机信号
on-hook signal [通信] 挂机信号
on-hook signal CBK 挂机信号
off hook signal 摘机信号
signal on hook 终话信号
signal off-hook 答话信号
Riggers and signal persons also need standard training and testing to ensure safety under the hook.
装配工人和发信号的人也需要标准的培训和测试，以确保安全下钩。
How is it then that uncertified and untrained people are allowed to signal and rig under the hook of a licensed or certified operator?
怎么能允许那么无证和未受过训练的人来代替有工作证或经核证的操作者呢？
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