Dynamic vs. static information, in a sense, is the only difference between a passive RFID and this device. In a sense, this could easily be made static/analog

Dynamic vs. static information, in a sense, is the only difference between a passive RFID and this device. In a sense, this could easily be made static/analog if you used some resonant filters. Take for example, a filter that operates at 1khz and 3khz. You radiate this device and get 1khz and 3khz tones back. Now take another one resonant filter at 7khz, and you get 1, 3, and 7, or 1, 3, 5, or 1,5,11, etc... You know have a unique passive, static identification technology. And this could have been done in 1945.