A transponder is an electronic device used to wirelessly receive and transmit electrical signals. Fittingly, its name is also derived from the words “transmitter” and “responder”. It was originally designed to be attached to an object that needed to be located, and some are still used that way today.
A transponder is a device that acts as both a transmitter and a transponder and is used to wirelessly receive and transmit electrical signals.
This device works by receiving a signal, called an “interrogator” because it effectively “asks” for information, and then automatically transmits a radio wave at a predetermined frequency. To transmit a signal at a different frequency than the one received, a frequency converter is incorporated. By receiving and transmitting on different frequencies, the two signals can be detected simultaneously.
A transponder key.
The first use of a transponder was on an aircraft during World War II, as part of the Identify Friend or Foe (IFF) system. By responding to secret interrogation frequencies, pilots could tell radar operators that they were friendly aircraft.
In aviation, transponders transmit the position and identity of an aircraft.
These devices are still common today in military and commercial aviation. They receive a signal from the ground and automatically respond with an identification code for air traffic controllers, as well as altitude information. In aeronautical applications, they are also configured to amplify the signal and make the aircraft more visible on radar.
Commercial aircraft transponders transmit their operator and flight identification numbers to air traffic control centers.
They are also used to measure distances by calculating the time between sending the interrogator signal and receiving the transponder signal. For example, sonar devices are used to mark positions underwater, calculate depth, and track positions.
It may seem like a technology that the average consumer never uses, but while it used to be that way, it isn’t anymore. The modern traveler probably has at least one transmitter in his car, probably mounted on the windshield or dash. They are for roads that use electronic toll systems that calculate the amount of the toll to be paid and complete the transaction without the driver having to lower the window. Some newer cars are also equipped with cars that operators can use to locate the vehicle in an emergency. Cell phones use a similar, though smaller, chip to send the phone’s location if you used to call an emergency number.
Even watching television from time to time involves the use of these devices. A network can connect its terrestrial satellites to communications satellites orbiting Earth, send multiple channels of digitally compressed video and audio to a single onboard transponder, and local stations can pick up the program and rebroadcast it locally, pointing to the appropriate dish based on the floor.
Communications satellites carry transponders.
