off hook meaning in English

离钩
数据机占线
脱钩，挂机(指示灯),占线指示
运算码；操作码
摘机

Interface circuits include auto - routing , load switch , polarity - reverting signal inverting and on - off hook checking
端口电路包括自动路由切换，负载转换，反极跳转，摘挂机检测等部分。
They fulfill communication with the gsm modem , read ring signal , and check on - off hook timely respectively
分别执行与无线通信模块的通信，读取来电信号，定时查询话机的摘挂机状态功能。