Noun
transponder (plural transponders)
A radar or radio transceiver that transmits some signal in response to receiving a predetermined signal.
Synonym: (slang) parrot
“Additionally, customers who receive a Toll Enforcement Invoice and wish to open a SunPass account can go online at http://www.SunPass.com to pay the invoice, purchase a transponder, establish the account and receive the lower SunPass toll rate.” Source: Internet
A communications satellite is an artificial satellite that relays and amplifies radio telecommunications signals via a transponder ; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Source: Internet
As the radar beam passes over the aircraft, the transponder is triggered to respond with both the 4-digit code, and also, if Mode ‘Charlie’ is selected, a read-back of the aircraft’s current altitude above mean sea level. Source: Internet
"At the start of the scaled QRA response, civilian air traffic controllers might see on their screens an aircraft behaving erratically, not responding to their radio calls, or note that it’s transmitting a distress signal through its transponder. Source: Internet
Depending on the category of airspace in which the flight is being conducted, VFR aircraft may be required to have a transponder to help Air Traffic Control identify the aircraft on radar in order that ATC can provide separation to IFR aircraft. Source: Internet
It also noted that the Ukrainian flight had done nothing out of the ordinary up until the missile launch, with its transponder and other data being broadcast. Source: Internet