Identification device

A reflective close-coupled identification system comprising:

• a first electrical circuit adapted to be connected to a source of alternating current and having a first inductive element;
• a second electrical circuit to be associated with the object to be identified and having a second inductive element adapted to be inductively coupled to said first inductive element for inducing an alternating voltage in said second circuit, all power consumed in said second circuit being derived from said first inductive element;
• means for selectively loading and unloading said second circuit in a predetermined time sequence over a predetermined period of time including a circuit operatively connected to said second inductive element and having a plurality of terminal pairs, the terminals of each pair being either conductively coupled for loading said second circuit when connected to said second inductive element or insulated from one another for unloading said second circuit when connected to said second inductive element, and means for sequentially connecting each of said terminal pairs to said second inductive element, said second circuit being loaded with the terminals of the terminal pair connected to said second inductive element are conductively coupled and said second circuit being unloaded when the terminals of the terminal pair connected to said second inductive element are insulated from one another;
• and
• sensor means responsive to said loading and unloading including detector means operatively connected to said source of alternating current for deriving a first signal having a characteristic with a magnitude variable with the instantaneous magnitude of the rate of said loading and unloading;
• averaging means operatively connected to said source of alternating current for deriving a second signal having a characteristic with a magnitude proportional to the average of said first signal characteristic magnitude;
• and subtracting means operatively connected to said detector means and said averaging means for producing an output signal with a characteristic having a magnitude proportional to the difference between said first and second signal characteristic magnitudes and varying in a time sequence dependent upon said predetermined time sequence, thereby providing such identification.