This is a scope capture of an analog ping with and without a receiver object placed on the pad. The upper trace shows the high amplitude of the pulse on the TX coil when the pad is empty. In the lower trace, when a receiver device is placed on the pad, the receive coil will absorb some of the energy from the short “ping” pulse so the voltage seen on the primary coil will be substantially reduced. When the TX side controller sees that the ping amplitude is loaded down, it then generates a longer “digital ping” which generates enough energy to wake up the RX side controller, which in turn sends out a specific packet of data to show the TX side that a valid RX is installed. The TX side will start to generate power out only after it receives a valid response from the receiver. The digital ping and authentication after an analog ping ensures that the TX pad does not start to generate output power if a passive object (such as keys, coins, or other metal items) are inadvertently left on the TX pad.