Month: August 2026

I got to wondering with ChatGPT after noticing some articles online about the transition to the new paper EZPassMA transponders. I also was curious what info ChatGPT would provide regarding their similarity to the chip embedded credit card technology.

Check out my Gemini conversation here.

I just was dealing with my EZPassMA and discovered that they are now going to a paper replacement for the transponder I have for new customers and replacements. I noticed that there was specific mention of not using batteries in the new stickers that are replacing the transponders. I am interested in knowing how this tecnology works without a battery in the sensor attached to the windshield.

It works by borrowing power from the toll equipment

The new E-ZPass MA sticker is a passive Radio Frequency Identification tag, usually shortened to RFID. It contains:

• A tiny electronic chip
• A very thin metallic antenna
• A paper or plastic backing
• Adhesive for attaching it to the windshield

Massachusetts began issuing these stickers to new customers and as replacements on March 1, 2026. Existing plastic transponders can continue operating. (WBUR)

What happens as you drive underneath a gantry

The overhead toll gantry sends out a powerful radio signal. When your vehicle enters that radio field:

1. The sticker’s antenna catches some radio energy.
2. A microscopic rectifier inside the chip converts that radio-frequency energy into direct-current electricity.
3. That tiny amount of electricity wakes the chip for a fraction of a second.
4. The chip retrieves its identification number from permanent memory.
5. It sends that number back to the gantry.

The identification number remains stored without electricity, much like information stored in flash memory.

But how does it transmit without power?

This is the clever part. The sticker does not generate a conventional radio transmission.

Instead, the chip rapidly changes the electrical load connected to its antenna. That changes how the incoming gantry signal is reflected. The reader detects those changing reflections and translates them into digital information.

This process is called backscatter communication. The National Institute of Standards and Technology describes it as reflecting or backscattering electromagnetic energy received from the reader. (NIST Computer Security Resource Center)

A simplified picture looks like this:

Toll gantry sends radio energy
             ↓
Sticker antenna collects energy
             ↓
Chip wakes and reads its ID
             ↓
Chip changes antenna reflection
             ↓
Gantry receives the reflected ID
             ↓
Computer matches ID to your E-ZPass account

A good electronics analogy

It is somewhat like combining a crystal radio with a radar reflector.

A crystal radio extracts enough energy from a radio signal to operate without a battery. The sticker similarly extracts energy from the gantry. However, instead of producing sound, it electronically changes its reflection to communicate its identification number.

Modern passive RFID tags use printed, etched or deposited conductive antennas. The reader’s radio waves power the chip, and the reader then receives the tag’s response. (Impinj)

Why the windshield position matters

The antenna is carefully designed for its operating frequency and surroundings. The windshield becomes part of that radio-frequency environment. Therefore, incorrect mounting, metallic window coatings or certain heated windshields can weaken the signal.

The sticker should be mounted exactly where the instructions specify. Unlike your removable plastic transponder, a sticker tag generally cannot be transferred between vehicles after installation. Removing it can damage the thin antenna or change its electrical tuning.

Does it transmit continuously?

No. Without a battery, it cannot sit there broadcasting its location. It normally remains electrically inactive until it enters a sufficiently strong field from a compatible reader.

That does not mean it is completely unreadable outside toll roads—a compatible reader placed close enough could potentially energize it. However, it does not independently beacon or transmit while your car is sitting in the driveway.

So the “paper transponder” really is a remarkably thin radio circuit. The expensive transmitter, power supply and sensitive receiver are all located on the toll gantry. The windshield sticker only needs enough circuitry to wake briefly and alter a reflected signal. Pretty ingenious stuff. 📡🚗

Are there any similarities to how the modern credit cards operate that you can “tap” to do your purchase?

Yes—the basic idea is very similar. Both can operate without their own battery by borrowing energy from the reader.

A tap-to-pay credit card contains a tiny chip and antenna. When you hold it near the payment terminal:

1. The terminal creates a radio-frequency field.
2. The card’s antenna captures energy from that field.
3. The energy briefly powers the card’s chip.
4. The chip and terminal exchange payment information.

The main differences are range, radio method, and security.

Tap-to-pay card

A contactless credit card normally uses Near Field Communication, or NFC, at 13.56 megahertz. It works through magnetic coupling—somewhat like a very loosely coupled transformer.

Its range is intentionally short, usually just a few centimeters. The chip also performs cryptographic calculations and generates transaction-specific information. It does not merely transmit your printed card number unchanged.

Toll sticker

A windshield toll sticker generally uses longer-range passive Radio Frequency Identification technology. Instead of transformer-like magnetic coupling, it usually captures energy from a radio wave and responds by changing how that signal reflects back toward the reader.

That allows the toll reader to identify it from several feet away while your vehicle is moving.

The simplest comparison

Tap-to-pay card:
Reader powers chip → chip performs secure transaction → card responds

Toll sticker:
Gantry powers chip → chip supplies tag identity → gantry bills account

So they are close technological cousins. Both are passive radio devices, but the credit card is designed for very close, secure financial communication, while the toll sticker is designed for fast identification at a much greater distance. 💳📡