I will try and answer your questions, but I am also going to put in some links within the forum that should answer most of your future questions.
But if I miss anything, just ask again
There is a lot to learn and it will take some reading on your part.
The NExT is a great device, because it has 2 chips in one,
The HF Chip ( 13.56MHz ) you can use on compatible access system, locks etc, but also you can write to it with your phone, in NDEF, things like Business card, address, URLs, etc see below.
these apps will be a good start for you Tag Writer Tag Info NFC Tools NFC Tools Pro
The T5577 is a LF (125kHz ) emulation chip, is the chip in the NExT and xEM. Emulation means it is capable of emulating different modes, which are still used all over the world and is incorporated in many access systems, so if you have an LF access system, chances are the T5577 can emulate it, such as EM41xx, EM4200, HID 1326 ProxCard, HID 1346, Indala…
However something to be aware of
Also, the T5577 is a great project implant and is compatible with
The mifare Classic is commonly found in hotel access systems, some workplaces and many Chinese locks
There are very few HF Chips with a changeable UID (NUID), but this is one that is.
the xM1 requires special tools to do this such as a Proxmark,
but if you don’t have one or access to one you can use this
