i am messing with some access card stuff. I have a flipper Zero and an RFID system. The system uses 125khz readers. The original cards are read as HID10301, and if I write T5577 FOB’s as HID10301 cards they work fine with the readers. BUT, if I write one of the blank T5577 cards with the “EM-Micro EM4100” format the readers do not even SEE the cards. Is the “EM-Micro EM4100” format on the flipper not the same 125khz frequency? Why are my readers not even seeing the cards? the flipper can re-read the cards after writing them just fine.
I’m not a pro in this subject but for me it seems like HID and EM4100 are more like “protocols”, not the “formats”. I mean, sure, they both have data in some format, but they also have their own ways to present themselves to a reader (which in turn expects only a certain type of tag) and start an exchange. About the frequency: it’s just a “channel” or a range of “channels” (like 125-134Khz) on which different types of tags/readers (and their respective protocols) can operate. Your reader even may “see” your copy but purposefully ignore it, as it is not obligated to give you an error message.
For short : lots of tags are operating in a LFRFID range, they have different protocols, which matters.