Editing Transponder (section)

==Other applications==

===Electronic toll collection===
[[Electronic toll collection]] systems such as [[E-ZPass]] in the eastern United States use [[RFID]] transponders to identify vehicles.<ref>{{Cite web |title=Understanding E-ZPass: The Ultimate Guide - Bestpass by Fleetworthy |url=https://bestpass.com/resources/blog/understanding-e-zpass |access-date=2025-03-08 |website=Understanding E-ZPass: The Ultimate Guide {{!}} Bestpass.com |language=English}}</ref>

===Lap timing===
Transponders are used in races for lap timing. A cable loop is dug into the race circuit near to the start/finish line. Each individual runner or car has an active transponder with a unique ID code. When the individual passes the start/finish line, the lap time and the racing position is shown on the score board.{{cn|date=May 2024}}

Passive and active RFID systems are used in [[motor sports]], and off-road events such as [[Enduro]] and [[Hare and Hound (Motorcycle Race)|Hare and Hounds]] racing, the riders have a transponder on their person, normally on their arm. When they complete a lap they swipe or touch the receiver which is connected to a computer and log their lap time.{{cn|date=May 2024}}

[[NASCAR]] uses transponders and cable loops placed at numerous points around the track to determine the lineup during a caution period. This system replaced a dangerous [[Racing back to the caution|race back to the start-finish line]].{{cn|date=May 2024}}

===Car keys===
Many modern automobiles have keys with transponders hidden inside the plastic head of the key. The user of the car may not even be aware that the transponder is there, because there are no buttons to press. When a key is inserted into the ignition lock cylinder and turned, the car's computer sends a signal to the transponder. Unless the transponder replies with a valid code, the computer will not allow the engine to be started. Transponder keys have no battery; they are energized by the signal itself.<ref>{{Cite web |url=http://carlocksmith.co/7-how-does-transponder-car-key-work.html |title=HOW DOES TRANSPONDER CAR KEY WORK? |date=19 February 2015 |access-date=2 May 2019 |archive-date=2 May 2019 |archive-url=https://web.archive.org/web/20190502135641/http://carlocksmith.co/7-how-does-transponder-car-key-work.html |url-status=dead }}</ref><ref>{{Cite web | url=http://www.rfid-handbook.de/downloads/E2E_chapter03-rfid-handbook.pdf | title=Fundamental Operating Principles | website=www.rfid-handbook.de | access-date=2024-07-26}}</ref>
===Gated communities===
Transponders may also be used by residents to enter their [[gated community|gated communities]].{{cn|date=May 2024}} 
However, having more than one transponder causes problems. If a resident's car with simple transponder is parked in the vicinity, any vehicle can come up to the automated gate, triggering the [[Identification friend or foe|gate interrogation signal]], which may get an acceptable response from the resident's car. Such units properly installed might involve [[beamforming]], unique transponders for each vehicle, or simply obliging vehicles to be stored away from the gate.{{cn|date=May 2024}}