Patent ID: 6170748
Filing Date: 2001-01-09
Classification: G06K

Abstract:
A method of storing and retrieving information representative of at least one characteristic of an object comprising the steps of:(a) attaching to said object a normally unpowered transponder having programmable memory for storing said information representative of at least one characteristic of said object;(b) generating a magnetic field burst signal containing a plurality of magnetic field cycles of a prescribed magnetic field variation frequency, such that said magnetic field burst signal impinges upon said transponder;(c) in response to receiving said magnetic field burst generated in step (b), causing said transponder to be powered from energy contained in said magnetic field burst signal; and(d) during a prescribed interval of time subsequent to receipt of said magnetic field burst in step (c), causing said transponder to emit a response magnetic field burst containing a plurality of cycles of said frequency, said prescribed interval of time being associated with information stored in said programmable memory; and whereinstep (b) comprises repetitively generating said magnetic field burst signal at successive burst intervals spaced apart in time by quiescent intervals therebetween;step (c) comprises storing energy contained in received successive magnetic field burst signals; andstep (d) comprises emitting successive response magnetic field bursts during respective intervals of time between said successive magnetic field bursts received in step (c), each respective interval of time being delayed relative to termination of an immediately preceding received magnetic field burst by a delay interval defined by information accessed from said programmable memory.