A tag is basically an electric circuit. If I were to add a switch to it, would it be possible to enable or disable the tag using that switch?
Yes, a tag is basically an electronic circuit. But the chip is an enclosed unit, so adding a switch is not as simple a matter as opening a wall in your home, cutting the wires to a light switch (with the power off, of course) and adding the switch. You would need to design and produce a chip that has the connections for an on-off switch. Designing, producing and testing such a chip for only a few thousand or even a few million units would likely be very expensive.
Some passive Near Field Communication (NFC) and ultrahigh-frequency (UHF) RFID chips do have an input-output port allowing you to connect the chip to another electronic device. You could, for example, wire an NFC tag to a thermostat and send signals to the tag in order to control the thermostat, which could then transmit information to the chip via the wired connection. But I don't think this can be used to create an on-off switch for the transponder itself, because the chip must be functioning in order to send commands to it that flow to the connected device.
Still, this might be worth exploring as a less expensive alternative to designing a custom chip.
—Mark Roberti, Founder and Editor, RFID Journal
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