this protocol is similar at the physical level to nfc (13.56  mhz carrier, basically an air-core transformer pair) and also qi's inductive energy transfer (100 khz-300 khz carrier). both modulate the receiver's coil load to communicate to the sender. some nfc tags can support simple processors and a handful of storage like this protocol. nfc also shares the physical security properties of "magnetic" communications like rubee, however nfc signals can be detected miles from the source. rubee signals are detectable at a maximum distance of from the source.