transponder

noun

tran·​spon·​der tran(t)-ˈspän-dər 

: a radio or radar set that upon receiving a designated signal emits a radio signal of its own and that is used especially for the detection, identification, and location of objects and in satellites for relaying communications signals

Did you know?

This word was coined during World War II by simply joining pieces of the words transmitter and responder. Transponders are basic to modern aviation and communications satellites, and they're finding new uses in fields such as medicine as well. But they're now also part of everyday life. The "E-ZPass" that lets you drive right through turnpike tollbooths is a transponder, and the car you're driving may not even start unless it recognizes the signal from your personal key's transponder. In a big crowded foot race, you may carry a tiny transponder on your shoe that records when you cross both the starting line and the finish line.

Examples of transponder in a Sentence

Recent Examples on the Web

Now, this is important because in places like the United States, many aircraft don’t and aren’t required to carry a transponder, right? —IEEE Spectrum, 17 Apr. 2024

Additionally, the city has been equipping some emergency vehicles with transponders that give LAFD vehicles green lights along their route, a program that could be expanded. —Ryan Fonseca, Los Angeles Times, 28 Feb. 2024

Word History

Etymology

transmitter + responder

First Known Use

circa 1944, in the meaning defined above