OK, so here’s a serious question. How does the stupid e-Tag stickers on the cars/motorcycles work? now for accessing my building’s parking space I need to use that sticker which I guess sends some radio frequency that is read by the sensor that lifts the bar.
The thing is that it’s not battery powered. So there are two options, I guess:
the sticker has something in its circuit that converts the light into AC electricity and that powers some transmitter
the reader sends some frequency that excites some component in the sticker that produces the radio frequency
I would say that num 1 makes more sense, but I THINK that not all the eTag stickers are placed over the headlights. But I might be wrong.
I might have googled this as well, but I prefer to give you some work.
It’s a passive RFID tag. Coiled up in the sticker is a long antenna that receives a pulse of radio wave energy from the reader, which is enough to power the system briefly. The hardware then reads the code number that’s embedded in the memory chip, and sends that ID code back to the reader. The reader then looks up the code in a big table and assigns that identity to the transaction (and then the system adds the amount to your account). All depends on high speed computing and data access.
How it works in your own building car park is a mystery. maybe they just scan it using the same kind o freader, and then assign the code they get back as your entry code for that building, without access to the billing data that the highway system uses.
So just to make it clear, there’s no photovoltaic cell or anything like that in that sticker, but it’s powered by the radio frequencies emitted by the reader at the door (or whatever).
EDIT: depending on the implementation, there are some serious security issues there…
Actually, we use passive RFIDs as our door security cards here. The system is encrypted by the vendor, so that you can’t just use any old reader to scan the card. The standard read protocols are ineffective, and there is some authorisation built into the chirp from the reader (which costs a friggin arm and a leg, of course available from the vendor only).
that’s one method of security built in, and i suspect there are many others.
passive RFIDs used as inventory control for library books, etc., are often not encrypted, because, why bother?
A passive tag is an RFID tag that does not contain a battery; the power is supplied by the reader. When radio waves from the reader are encountered by a passive rfid tag, the coiled antenna within the tag forms a magnetic field. The tag draws power from it, energizing the circuits in the tag. Passive RFID Tag (or Passive Tag)
@urodacus, I saw a few manta ray stingrays like 5 weeks ago in a beach near Keelung and although I did some research online I couldn’t identify the species. I wanted to ask someone but I know no one who could have an answer… and I just realized that you might know it!
A couple of peculiarities: they were pretty white (they blended perfectly with the sand bed) and they were or looked almost perfectly round shape, which is weird because in most of the pictures I found on internet the animal looks like a pentagon. While the colour may seem to be a good characteristic to ID them, it’s not really helpful, given that some or perhaps many species can and do adapt their color (colour) to match the environment’s, even if it takes days. As for the round shape, the closest things I found were… fresh water ones. I don’t think the water in that part of the shore was brackish, it was just normal sea water.
What else, what else… the tail was black or pretty dark IIRC. Size… small. How small? can’t remember now. Exact location? I can send you by PM if needed, but near Keelung.
More likely to be a stingray, as manta rays are bigger than you, and you’d kinda notice that. There are several species of stingray in Japan and Taiwan and more in Philippines, etc. They can look mostly round or oval but some have different front edge shapes. They are coloured to blend in with the sand as they spend a lot of time on the bottom.
OOOOPS, sorry, mind fart. I meant to write sting ray!!! I know what mantas and sting rays are, but I’m sick and sleepy these days and I don’t know what I write.
I have a question bothering me recently and didn’t know where to ask. Then I reminded this nice thread, so I’d try to poke the incredible mind of @urodacus…
Why every hair salon in Taiwan has a barber pole in front of it? How it became so popular here?
And since we are at it, what’s the origin on the barber pole?
“In Renaissance-era Amsterdam, the surgeons used the colored stripes to indicate that they were prepared to bleed their patients (red), set bones or pull teeth (white), or give a shave if nothing more urgent was needed (blue).”
More pertinent to Taiwan, it was also traditionally the sign of a brothel in Western history.
Probably used for barbershops in East Asia because it was something Westerners who couldn’t read the local script could easily associate with service- of either kind.
My father was in Taipei a few times on business in the 1980s, and every time he visits now he insists on reminding the rest of us that barber poles are for brothels, and the colors and patterns on the pole indicate what sorts of services are offered. I’ve never figured out how much of this was accurate back in the 80s, how much he’s making stuff up, and how much some prankster in the 80s was playing games with the dumb foreigner.
No idea - I have not asked follow-up questions. Ever. The details are either lost in the mists of time, or considered improper to explain to his wife and son. Fine with me either way!