RFID reader technology
http://www.circuitnet.com/experts/39998.html  juki uses an array of antennas (presumably one per slot)  perhaps wired in a matrix like this.

the antennas could perhaops be drum inductors (they's haver to be something with a small field so as to be sufficiently selective to only see one tag)







simulate this circuit &ndash; Schematic created using CircuitLab