Additionally to the active and passive mode, there are two different roles a device can play in NFC communication. NFC is based on a message and reply concept. This means one device A sends a message to another device B and device B sends back a reply. It is not possible for device B to send any data to device A without first receiving some message from device A, to which it could reply. The role of the device A which starts the data exchange is called initiator, the role of the other device is called target. The following Table 2: lists all possible combinations of this role with respect to the active or passive mode.