indicator cock

例句：

1. 1.The device is used to indicate the presence of a specific chemical in the air.
   这个装置用于指示空气中特定化学物质的存在。
2. 2.The indicator cock was used to signal the start of the race.
   指示器cock被用来信号比赛的开始。
3. 3. The technician carefully adjusted the indicator cock to ensure accurate readings.
   技术人员小心地调整指示器cock，以确保准确的读数。