Process and apparatus for identification of objects

In a process for identifying objects marked by a magnetic band or thin filament by detecting the passage of the magnetic band in a detection zone comprising at least one framework with an excitation coil fed with alternating current to produce an alternating magnetic field and a detecting coil balanced with the excitation coil such that no signal normally will appear in the absence of a magnetic body in proximity to the framework, the passage through or in proximity to the framework of an object carrying a magnetic band producing for each alternation of the excitation field an unbalance in the detecting coil and the appearance of a signal fed to an apparatus for the detection and measurement in phase with respect to the excitation field, the improvement comprising forming a reference code for an object by selectively dividing the magnetic band at a variable predetermined location by cuts of variable predetermined extent, such that at the time of passage of the band proximate the detection zone signals of variable amplitudes also predetermined are produced, and decoding the signals in the detection apparatus by measurement of said amplitudes, the object being marked with a plurality of bands or thin magnetic filaments each having different hysteresis loops characterized by different coercive fields thus permitting assignment to each object of a reference code with as many characters as bands or filaments utilized and respectively assigning each character of the reference code to a band or filament in the order of the values of their respective coercive fields, the signal corresponding to each band appearing then in the detection apparatus in the same order of dephasing as the order of the coercive fields and each with amplitudes corresponding to the values assigned at the time of coding thereby reporducing the complete code in arrangement and amplitude.