Abstract: An apparatus for validating bank notes and other valuable documents having magnetic characteristics which provide a predefined signature. The validator comprises a receptor for receiving a bank note. The bank note is inserted in the receptor and pulled through a passage-way which includes magnetic and optical sensing chambers. The magnetic sensing chamber includes a sensor and a magnetic head for generating a magnetic field. When the bank note passes through the magnetic sensing chamber, the magnetic characteristics of the bank note affect the magnetic field and the sensor produces an output signal corresponding to the magnetic field. The validator includes a processor which processes the output signal to produce a bank note frequency value correlated to the signature of the bank note. The processor validates the bank note by comparing the frequency value to a base-line frequency value and determining the deviation from the base-line value.