transponder
n. 异频雷达收发机，（发射机）应答器，转发器
例句
In Singapore, every car is fitted with a digital transponder that triggers automatic tollbooths as it passes.
在新加坡，每辆轿车上都装有一台在通过时自动触发过路收费亭的数字式异频雷达收发机。
《柯林斯英汉双解大词典》
The sentry guns will not fire at anyone wearing a badge transponder.
这样哨位机枪塔就不会向任何一位身着徽章的人开火。
It will have a "special transponder" that will be able to find signals from emergency beacons.
它将配备一个“特制应答机”，能够发现应急信标的信号。
