tran·​spon·​der | \ tran(t)-ˈspän-dər How to pronounce transponder (audio) \

Definition of transponder

: 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

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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 The Audi e-tron was the first to get the transponder sourced from Gentex, the same company that gave us self-dimming rearview mirrors. Motormouth Bob Weber, Star Tribune, 4 June 2021 Fishermen might put the ID of an oil tanker on a transponder for their nets to warn away other vessels. Adrian Bridgwater, Forbes, 19 Apr. 2021 The agency in recent days has started processing notices for more video tolls — in which motorists without an E-ZPass transponder pay by mail — that were incurred back to August. Washington Post, 20 Mar. 2021 Each car has a tiny transponder inside and wires are embedded by the start/finish line. Dana Hunsinger Benbow, The Indianapolis Star, 30 May 2021 For example, people traveling on Maryland toll roads without an E-ZPass transponder are billed by mail. Washington Post, 1 May 2021 In any event, dragging those four fighters to the South China Sea’s hot zone required four Air Force KC-135 tankers, each of which had its radio transponder on and thus was visible on public plane-tracking websites. David Axe, Forbes, 16 Apr. 2021 Most of the debt to the MDTA includes video toll late fees — in which motorists without an E-ZPass transponder pay by mail. Washington Post, 1 May 2021 Drivers use a SunPass transponder to pay for the lanes, which range from 50 cents to an estimated $10.50, depending on the time of day, the amount of traffic and distance traveled in the express lanes. Wells Dusenbury,, 30 Apr. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'transponder.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of transponder

circa 1944, in the meaning defined above

History and Etymology for transponder

transmitter + responder

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Learn More About transponder

Time Traveler for transponder

Time Traveler

The first known use of transponder was circa 1944

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Statistics for transponder

Last Updated

14 Jun 2021

Cite this Entry

“Transponder.” Dictionary, Merriam-Webster, Accessed 24 Jun. 2021.

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More Definitions for transponder



English Language Learners Definition of transponder

technical : a device that receives a radio signal and sends out a signal in response and that is used especially to show the location of something (such as an airplane)

More from Merriam-Webster on transponder

Nglish: Translation of transponder for Spanish Speakers Encyclopedia article about transponder


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