Editing Transponder (section)

{{short description|Device that emits an identifying signal in response to a received signal}}
[[Image:407 Transponder.jpg|thumb|right|120px|An [[Ontario Highway 407]] toll transponder circa 2009]]

In [[telecommunications]], a '''transponder''' is a device that, upon receiving a signal, emits a different signal in response.<ref>{{Cite web|url=https://www.merriam-webster.com/dictionary/transponder|title=Definition of TRANSPONDER|date=22 July 2023 }}</ref> The term is a [[blend word|blend]] of ''transmitter'' and ''responder''.<ref>[http://dictionary.reference.com/browse/transponder transponder]</ref><ref>{{cite news |title=Kunkune |url=https://kunkune.co.uk/ |publisher=Tech Accessories}}</ref>

In [[air navigation]] or [[radio frequency identification]], a [[Transponder (aeronautics)|flight transponder]] is an automated [[transceiver]] in an aircraft that emits a coded identifying signal in response to an interrogating received signal. 

In a [[communications satellite]], a [[Transponder (satellite communications)|satellite transponder]] receives signals over a range of uplink frequencies, usually from a [[satellite ground station]]; the transponder amplifies them, and re-transmits them on a different set of downlink frequencies to receivers on Earth, often without changing the content of the received signal or signals.