Metal strip sensing system for banknote testing

摘要

The banknote (1) with an integral metal strip (2) is fed between two arrays of electrodes (4-7), one of which (4,5) act as transmitting electrodes that connect alternately with frequency generators (8, 9) generating outputs with different amplitudes. The receiving electrodes (6, 7) connect with a test circuit and the received signal is in a modulated from dependent upon the presence or a absence of the metal strip. The test unit generates an output indicating the result.