On Wed, Apr 10, 2002 at 10:59:32AM -0700, Tim May wrote:
| On Wednesday, April 10, 2002, at 09:27 AM, Trei, Peter wrote:
| >> For paper money failure rates will probably be high anyway.
| So, if in fact we _are_ talking about each $20 bill having such a
| transponder, then why are our arguments about how easy it will be to
| shield against remote probing not valid? Put the money in a foil packet,
| or fold it over, or carry it in a stack, or in a standard metal
| briefcase, and I _guarantee_ that detecting it from afar will be
| extremely difficult.
|
| If a stack of bills containing these transponders are supposed to be
| read from afar, way beyond what a "valid bill detector" is likely to be
| engineered to do, I'd like to see the physics worked out.
|
| (A stack of bills, or cards, will have extremely poor radiation patterns
| from any but the top or bottom bill, and probably their patterns won't
| be good either.)
Does it matter? Intuitively, you broadcast a radio signal, and pick
up from that where the largest clusters of bills are. Repeat several
times if needed. You don't care about signal accuracy, just
magnitude. You then decide if the people with wads of cash look like
an easy mugging target.
Adam
--
"It is seldom that liberty of any kind is lost all at once."
-Hume
