Vending machines use a variety of methods to validate and determine the value of a banknote, including:

* **Magentism**- Bank notes are written in magnetic inks that give each type of note a distinctive magnetic field that the machine can detect.
* **Electrical Conductivity**- The rate at which bills conduct electricity may vary depending on the specific denomination.
* **Fluorescence**- Different denominations might have distinct fluorescent properties, which can be determined through fluorescent scanning.
* **Digital Photography**- With modern technology, the note can be visually scanned and compared with a database of standard notes.
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