transponder

American  

[tran-spon-der] / trænˈspɒn dər /

Or transpondor

noun

1. a radio, radar, or sonar transceiver that automatically transmits a signal upon reception of a designated incoming signal.

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transponder British  

/ trænˈspɒndə /

noun

1. a type of radio or radar transmitter-receiver that transmits signals automatically when it receives predetermined signals

2. the receiver and transmitter in a communications or broadcast satellite, relaying received signals back to earth

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transponder Scientific  

/ trăn-spŏn′dər /

1. A radio or radar transmitter and receiver that responds to an incoming signal either by broadcasting its own predetermined signal (as in aircraft identification systems) or by relaying the incoming signal at a different frequency (as in satellite communications).

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Etymology

Origin of transponder

First recorded in 1940–45; trans(mitter) + (res)ponder

Example Sentences

They said the plane was broadcasting its military number through the transponder, but the boat targeted in the strike likely lacked the equipment to read the radio signal identifying the plane.

From Salon

Two sanctioned oil tankers shut off their transponders earlier this month and powered to a meetup point, drawing alongside each other in the Sea of Japan.

From The Wall Street Journal

The ships are known to turn off their transponders, fake their locations, fly false flags and conduct hidden ship-to-ship transfers in poorly monitored waters to disguise the origin of their oil.

From The Wall Street Journal

One-third of Arctic shipping traffic now consists of “dark fleet” tankers with spotty insurance, disabled transponders and the maritime equivalent of fake IDs.

From MarketWatch

It said: "The ship, initially flying a false flag, turned off its transponders while at sea and sought to reflag while being pursued."

From BBC