In addition to the signaling technologies used by near field communication technology, four tag types and two sets of active/passive roles exist. Tag types refer to the speed and compatibility between an NFC tag and NFC readers, and the roles define how active and passive devices respond during a NFC communication. Most often a URL will be embedded in a NFC tag. URLs take up only a small amount of memory, lowering the production cost of the NFC tags since many are placed on posters or other items that are thrown away later on. NFC tags can, however, hold nearly any type of information, though more memory costs more money.

Tag Types

• Type 1: Type 1 NFC tags have data collision protection and can be set to either read and rewrite capable or read-only. Read-only programming prevents the information from being changed or written over once embedded in the tag. Type 1 tags have 96 bytes of memory, enough for a URL or a small amount of data. The tag’s memory can expand to a larger size as needed. The low price makes type 1 tags to ideal choice for most near field communication needs.

• Type 2: Type 2 NFC tags also have data collision protection and can be rewriteable or read-only. They start at 48 bytes of memory, half of what the type 1 tags can hold, but can expand to be as large as a type 1 tag. Communication speeds are the same for tag types 1 and 2.

• Type 3: Also equipped with data collision protection, NFC tag type 3 has larger memory and faster speeds than tag types 1 and 2. This tag is part of the FeliCa system. The bigger size lets it hold more complex codes beyond URLs, but it costs more to create each tag.

• Type 4: Type 4 NFC tags can use either NFC-A or NFC-B communication and have data collision protection. The tag is set as either rewritable or read-only when manufactured and this setting cannot be changed by the user, unlike the other NFC tags which can be altered at a later date. The tag holds 32 Kbytes in memory and has faster speeds than the other tags.

In addition to the four tag types, four modes of operation exist. The modes – reader/writer, card, initiator, and target – describe what role a device or tag is playing in an NFC transaction. Devices can switch between more than one role depending on the transaction being processed.

NFC Basic Roles

• Reader/Writer and Card – Typically a transaction occurs between an active device that sends out signals and receives information and a passive device that simply sends the information and does not receive anything other than instructions on what data to reply with. The reader/writer is the smartphone serving as the active device and the card is the NFC tag serving as the passive device. Smartphones can take on the role of card, however, when they act as a credit card for contactless payments. Then the credit card reader becomes the reader/writer and the smartphone serves as the passive card device.

• Initiator and Target – NFC technology has a major advantage over other technologies such as RFID. NFC can create peer-to-peer sharing between two phones. In this case, the phone making the connection or sending an invitation is the initiator and the phone receiving the instructions and sending back information is the target. Yet both phones can serve both roles by switching back and forth depending on what transmission is being sent, though this requires a higher level of technology.