Mechanisms that allow data to be communicated between two devices generally use power at both the transmitting and receiving ends (supplied through wall power or a battery), and a wired or wireless communication channel between the devices. Some devices, such as Radio Frequency Identification (RFID) devices, can send data outward without being tethered to a power source, and without what would normally be regarded as a communication channel between itself and the recipient of the data. Such devices are powered by energy that is broadcast (e.g., in the form of electromagnetic waves in the radio frequency, in the case of RFID). These devices reflect data in response to the broadcast of energy. The devices typically have a fixed item of data that is reflected when the device is energized. Switched versions of such devices have been proposed, where an energized device would either transmit data, or not, depending on whether the switch is open or closed.
One issue that arises is what types of applications can be made of switched devices that transmit data. Such devices could be used to implement a variety of functionalities. Systems that facilitate a broad range of uses of such data-transmitting devices generally have not been realized.