An RFID system consists of two main parts: the reader station, shown on the left-hand side and the RFID Tag, shown on the right. The tag can be an ISO card, a key fob, a coin, or an animal tag such as an ear tag or glass transponder. These two constituents communicate through the air via a magnetic field. For this reason, both tag and reader are equipped with a coil. The reader generates a field in the range of 100kHz to 150kHz. Two frequencies are predominant in this range: 125kHz for access control solutions and 134.2kHz for animal ID solutions. The generated field transmits energy, data and commands to the tag. Within the chip, a dedicated block generates the internal supply voltage and the internal clock, derived from the field clock. A logic portion decodes the commands or data transmitted by the reader and initiates the related actions. This may be read or write commands or system and configuration commands. For this purpose, the field protocol includes phases where the field is switched off, which causes so-called gaps where the tags synchronize. Reading from the tag is more frequent. If not sending data or commands, the reader's field is on and it monitors for modulation from the tag in the field. The reader is able to detect ASK (Amplitude Shift Keying) modulation and to supply the decoded data to a connected microcontroller. A memory (addressed by the logic block) is typical for an RFID application. To support the Write functionality, sufficient programming voltage is generated by an internal charge pump. Password and lock features provide security to protect the information.