# How does the EZ Tag work? **URL:** \ **Category:** Factual Questions\ **Created:** [July 23, 2000, 3:54pm UTC](https://boards.straightdope.com/t/how-does-the-ez-tag-work/26551 "2000-07-23T15:54:29Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![light\_strand](https://avatars.discourse-cdn.com/v4/letter/l/a6a055/32.png) [@light\_strand](https://boards.straightdope.com/u/light_strand)\ **Post date:** [July 23, 2000, 3:54pm UTC](https://boards.straightdope.com/t/how-does-the-ez-tag-work/26551/1 "2000-07-23T15:54:29Z")
I have an EZ tag on my car for the toll roads. How does this thing work? How do they make it unique to each vehicle? Is the tag on my car the transmitter, or the receiver? How come it works at such high speeds? I need to know! ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [July 23, 2000, 4:10pm UTC](https://boards.straightdope.com/t/how-does-the-ez-tag-work/26551/2 "2000-07-23T16:10:02Z")
My understanding is the ones for the Kansas turnpike are radio oscillators. When you get close enough to an RF source at the booth, a little printed circuit within the tag oscillates at a certain frequency - sorta like “Tattle-Tape”-type stickers which are put in library books. The system works pretty fast, so you could be going a decent speed through the gate. The reason they slow you down is so if the receiver doesn’t get the signal it expects they can drop the gate (“lower the boom”, so to speak) and catch you. To the best of my knowledge, the tags have no idea which vehicle they are in, and I don’t know how they could make it unique to a vehicle. What keeps an 18-wheeler driver from buying a tag for his/her car and using it for their truck I do not know. Is it a hang tag or on stucj to your bumper? ---
**Author:** ![Mr.Blue\_Sky](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@Mr.Blue\_Sky](https://boards.straightdope.com/u/Mr.Blue_Sky)\ **Post date:** [July 23, 2000, 4:10pm UTC](https://boards.straightdope.com/t/how-does-the-ez-tag-work/26551/3 "2000-07-23T16:10:57Z")
IIRC, you have the transmitter in your car. On a nearby utility pole would be a transceiver. When you go by, your unit is picked up by the transceiver and sends the info back to the home office where your account is updated. Your transmitter is always transmitting, but it has a very short range so that you don’t interfere with other type devices. Several gasoline companies now use this technology when you fill up your car. Just wave the unit at the gas pump, fill up, and off you go. ---
**Author:** ![light\_strand](https://avatars.discourse-cdn.com/v4/letter/l/a6a055/32.png) [@light\_strand](https://boards.straightdope.com/u/light_strand)\ **Post date:** [July 23, 2000, 4:20pm UTC](https://boards.straightdope.com/t/how-does-the-ez-tag-work/26551/4 "2000-07-23T16:20:28Z")
**Anthracite** It’s a credit card sized device that attaches to the windshield. I suppose you can move it from veihicle to vehicle, but it’s unique to my credit card account. I also found that I can go through as fast as 70mph and it still reads. It doesn’t read if you go much faster than that. We don’t have gates here so you can really scoot through the tolls. **Mr. Blue Sky** Every time I go through I can’t help but think it’d be useful in tennis. You wouldn’t need line judges if they fitted a tennis ball with a similer device. or would you? ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [July 23, 2000, 4:45pm UTC](https://boards.straightdope.com/t/how-does-the-ez-tag-work/26551/5 "2000-07-23T16:45:38Z")
This from [http://www.ezpass.com/faq.shtml](http://www.ezpass.com/faq.shtml) : Q. I sometimes pull a trailer with my vehicle. Can I still use my tag? ``` A. Yes. In this instance the equipment in the lane will identify that your vehicle is pulling a trailer and charge you accordingly. However, if you think this will be a regular occurrence, you should call the Customer Service Center and have them send you a tag programmed for the vehicle classification you use most frequently. You should never use your tag in a vehicle type other than the one you initially requested (ie. Car tag in a tractor-trailer) ``` * * * Each tag has a unique ID burned into it. It’s not always transmitting- it wakes up when it receives a signal from the toll booth. It operates at 915 MHz. There’s a huge amount of detail about how it all works here: [http://www.ettm.com/focus\_pa/etcfocus\_panynj.html#vendors](http://www.ettm.com/focus_pa/etcfocus_panynj.html#vendors) Arjuna34 ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [July 23, 2000, 4:47pm UTC](https://boards.straightdope.com/t/how-does-the-ez-tag-work/26551/6 "2000-07-23T16:47:11Z")
> [@](#): > > ## \*Originally posted by Arjuna34 \* \*\* > > Each tag has a unique ID burned into it. It’s not always transmitting- it wakes up when it receives a signal from the toll booth. It operates at 915 MHz. There’s a huge amount of detail about how it all works here: [http://www.ettm.com/focus\_pa/etcfocus\_panynj.html#vendors](http://www.ettm.com/focus_pa/etcfocus_panynj.html#vendors) > > Arjuna34 \*\* Hmm, that link puts you down near the bottom of the page. You’ll have to scroll up to see how it works. Arjuna34 ---
**Author:** ![stuyguy](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@stuyguy](https://boards.straightdope.com/u/stuyguy)\ **Post date:** [July 23, 2000, 4:58pm UTC](https://boards.straightdope.com/t/how-does-the-ez-tag-work/26551/7 "2000-07-23T16:58:48Z")
Hijack: Here in the northeast we have EZ-PASS. As a general rule you are required to go through the toll gates at 5 MPH; some gates have drop-arm barriers, some do not. Naturally, I thought the slow speed limit was so that the detector would have time to scan the tag. But no. I read somewhere that the tags are designed to work at some pretty fast speeds. The reason that thousands and thousands of drivers have to go from 60 to 5 to 60 again is because the Goddamn toll booth workers are concerned they will be hit by cars! 45 mph is good enough for road crews, but not tolltakers. Besides, aren’t all those toll booths connected underneath by a tunnel? If they’re so afraid, let them use that instead of strolling out into traffic. ---
**Author:** ![Jophiel](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jophiel/32/66_2.png) [@Jophiel](https://boards.straightdope.com/u/Jophiel)\ **Post date:** [July 23, 2000, 6:29pm UTC](https://boards.straightdope.com/t/how-does-the-ez-tag-work/26551/8 "2000-07-23T18:29:18Z")
Here in Illinois, it’s the I-Pass and there’s generally a few lanes (1-3 depending on the tollway) reserved just for them although I think most will let you use the I-Pass through any toll. You just want the far left reserved ones so you’re not stuck behind some guy fishing for fourty cents in pennies. Anyway, most of them now have a speed of 35-40mph if memory serves. I’ve gone through them faster than that without issue, but when they first came out, it was a mere 10-15mph.