12-22-2012 08:41 AM
My understanding is that an RFID in a card (i.e. ExpressPay, Blink, etc.) is a tiny radio emitter. My question is - where does it get power to constantly send out a radio signal. Does it have a small battery? I couldn't find anything on the web...
12-23-2012 01:31 PM
"For RFID devices such as blink cards, engineers have harnessed induction. Each blink card contains a small microchip as well as a wire loop. The blink terminal gives off a magnetic field in the area around it. When a blink card gets close enough, the wire loop enters the terminal's field, causing induction. The voltage generated by the induction powers the microchip. Without this process, called inductive coupling, each blink card would have to carry its own power supply in the form of a battery, which would add bulk and weight and could eventually run out of power. Because the power is supplied by the terminal, the blink system is known as a passive system."