tran·spon·der | \tran(t)-ˈspän-dər \

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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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

The authority will verify a driver’s account of the cause and location of damage, including through toll-transponder data. Kevin Spear,, "I-4 construction nightmares: Drivers seeking payment for car damage face daunting odds," 13 July 2018 About 4 million of those each month do not have transponders. Adam Vaccaro,, "1.3 million cars have slipped through Mass. toll gantries," 24 May 2018 But not all ships are required to carry transponders, and some captains switch them off. The Economist, "Avast, me hearties," 5 July 2018 But nearly 65 percent of tolls paid by transponders on authority roads, which include S.R. 408, 417 and 429, are with SunPass devices. Kevin Spear,, "SunPass accounts being restored after weeks of a botched system upgrade," 6 July 2018 The agency said 467 people were using the EZ-Pass transponders for free. Kay Lazar,, "Despite warning, MassDOT continued toll-free perk for workers, retirees," 8 June 2018 Metro has spent a year developing an automated system designed to count the number of occupants in a car and issue a ticket if the transponder setting does not match. Laura J. Nelson,, "Metro wants to end free rides for clean-air vehicles in toll lanes," 25 Apr. 2018 After the trip, due to a design defect, the transponder was not able to power back up. Jason Daley, Smithsonian, "Amateur Astronomer Finds Long-Lost NASA Satellite," 29 Jan. 2018 Approximately 250 miles north of the Libyan coastline, the pilots turned south, switched off their transponders, and disappeared from air-traffic-control radar. William Langewiesche, The Atlantic, "An Extraordinarily Expensive Way to Fight ISIS," 21 June 2018

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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Last Updated

20 Sep 2018

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Time Traveler for transponder

The first known use of transponder was circa 1944

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English Language Learners Definition of transponder

: 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)

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