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Simple Science: How E-ZPass transponders operate

 – Photo by null

Drivers heading down the Garden State Parkway may find that white-and-purple E-ZPass signs are becoming increasingly prevalent, helping to reduce toll lines and streamline payments.

E-ZPass devices are radio-frequency identification transponders. They emit radio waves that an antenna attached to toll booths can read, which reduces the need for human operators or loose change.

The receiver at a toll booth broadcasts a signal to the transponder, which then “replies” with identifying information. This tells the booth’s computer to let the vehicle go through.

The transponder itself is connected to its owner’s E-ZPass account. The company charges the transponder’s owner the appropriate toll, which it then pays to the booth’s owner.

Because the receivers are designed to read any and all E-ZPass transponders, they can read multiple devices within a single vehicle. In other words, if there are two devices in a car, both will be charged for passing through a booth

Wrapping one in foil may prevent this from happening, if a person is transporting multiple tags.

The use of E-ZPass transponders may have lead to a noticeable decrease in the amount of pollution near toll booths. Since the system is automatic, cars spend less time idling in line while drivers pay human operators their tolls.

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