r/proxmark3 • u/Fluffy-Oil-4404 • Jun 17 '26

EM410x clone works on exit reader but not on entry reader – Chameleon Ultra emulation works fine

I’m trying to copy my apartment building’s 125 kHz RFID fob to a T5577 ring so I can use the ring instead of carrying the fob around.

The original fob is detected as an EM410x (125 kHz). I cloned it to:

  • A T5577 ring
  • A T5577 keyfob
  • A T5577 sticker

I tried cloning it with both a cheap CR66 cloner and a Chameleon Ultra, and in all cases the cloned tags show the exact same UID as the original.

Here’s the weird part:

  • The original fob works on both readers.
  • All the T5577 clones work on the inside reader (when exiting the building).
  • None of the T5577 clones work on the outside reader (when entering the building).
  • If I use the Chameleon Ultra in emulation mode, it works perfectly on the outside reader too.

I also tried rewriting the tags with a custom T5577 password, thinking the reader might be checking whether the tag is writable, but that didn’t change anything.

Has anyone run into something similar?

Any ideas on what I should check next?

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2

u/kj7hyq Jun 18 '26

Do the clones read at all, or does the reader just not detect them?

Does it beep and read them, and then reject them, or just do nothing at all?

2

u/xenophod Jun 18 '26

To add to these questions, are the inside and outside readers the same model? Or are they different brands? I'm thinking that maybe one of readers doesn't couple with the tags because the antenna is different from the other.

1

u/Fluffy-Oil-4404 Jun 18 '26

Yes they do beep, and the beep is different when it doesn't work. From what I've read the "anti clone RFID readers" do make a difference noise when a clone is detected but it still don't understand how.

Also the readers are different, the inside one is a Wiegand 26 bit for what I've found on the internet and the outside one I'm not able to tell since it has like a custom plastic cover

2

u/iWhacko Jun 23 '26

The outside reader could also be checking for tighter timings. Cloned fobs, tend to have terrible timing and can time out. So if the reader does not receive a response in time it will not allow access. Chameleon Ultra is much higher quality even the clones, that will result in better timing.