Are there any RFID triggering devices?
Not RFID, but it’s quite often possible to trigger the passive-tag detectors using car keys. Take 2 keys side-by-side on your key ring, then slide them apart into a V-shape such that the notches are facing each other. Walk repeatedly through a detector, moving the keys slightly each time, until it goes off. Memorise this position for much future fun, hilarity, and bag-searching… (Put simply, the tags work by resonance stimulated by a field from the gates in the doorway, and if you get it right the gap between the teeth of the 2 keys matches the resonant frequency of a tag.
There are a ton of different things that fall under the term “RFID tag” and there are a ton of other technologies that look the same on the surface. First, the theft tags. Most of these don’t do any identifying, so I wouldn’t call them RFID. They’re just RF-detectable in some way. Some are just resonant circuits that “ring” at a particular frequency. Those usually have a small amount of nonlinearity added so that they emit harmonics as well, which makes it easier for the reader/gate (which is constantly sending out that particular frequency and listening for answering notes) to distinguish the tag from its own emissions. These are the tags that usually look like a square patch with a spirally trace, which is the antenna and the inductive part of the resonant circuit. (See.) (There’s a “magnetostriction” resonant tag technology out there too which i know nothing about.) Another kind I know of has a magnetic material with a very
